Update outdated visible content spec descriptions

This fixes some spec descriptions that were not fixed in https://gitlab.com/gitlab-org/gitlab-ce/merge_requests/7947.

See merge request !7971

Fix Backup::Manager#remove_old

Closes #25399

See merge request !7972

Fix typos in API doc examples

## What does this MR do?

Fixes a typo in the API docs. The `curl` examples in [build_triggers.md](doc/api/build_triggers.md) and [build_variables.md](doc/api/build_variables.md) all have a typo in the auth header. They all say `PRIVATE_TOKEN` when it should be `PRIVATE-TOKEN`.

## What are the relevant issue numbers?
Fixes #24565

See merge request !7514

Run builds with runners with tags gitlab-org and 2gb

## What does this MR do?

Added `gitlab-org` and `2gb` tags for jobs in `.gitlab-ci.yml`. So builds will be picked up by `gitlab-shared-runners-manager-X.gitlab.com runners`

## Are there points in the code the reviewer needs to double check?

Only `.gitlab-ci.yml`

## Why was this MR needed?

https://gitlab.com/gitlab-com/infrastructure/issues/714

## Screenshots (if relevant)


## Does this MR meet the acceptance criteria?

- [ ] [Changelog entry](https://docs.gitlab.com/ce/development/changelog.html) added
- [ ] [Documentation created/updated](https://gitlab.com/gitlab-org/gitlab-ce/blob/master/doc/development/doc_styleguide.md)
- [ ] API support added
- Tests
  - [ ] Added for this feature/bug
  - [ ] All builds are passing
- [ ] Conform by the [merge request performance guides](http://docs.gitlab.com/ce/development/merge_request_performance_guidelines.html)
- [ ] Conform by the [style guides](https://gitlab.com/gitlab-org/gitlab-ce/blob/master/CONTRIBUTING.md#style-guides)
- [ ] Branch has no merge conflicts with `master` (if it does - rebase it please)
- [ ] [Squashed related commits together](https://git-scm.com/book/en/Git-Tools-Rewriting-History#Squashing-Commits)

## What are the relevant issue numbers?

https://gitlab.com/gitlab-com/infrastructure/issues/714

See merge request !7757

Grapify the issues API

Related to #22928

See merge request !7968

Update GLU index for new report, broken links + typos

## What does this MR do?
Update text on GLU documentation for spelling and new State of DevOps book. 

/cc @axil

See merge request !7962

Bump Git version requirement to 2.8.4

Following gitlab-org/omnibus-gitlab!1108, the install doc and README should be updated too.

See merge request !7878

Bump gitlab-shell version to 4.0.3

See merge request !7953

Move admin hooks spinach to RSpec

https://gitlab.com/gitlab-org/gitlab-ce/issues/23036

See merge request !7942

Move admin logs spinach test to RSpec

https://gitlab.com/gitlab-org/gitlab-ce/issues/23036

See merge request !7945

UX Guide - add initial animation guidance

Adding guidance to our UX Guide around animation. This is to help us implement #24831 and add polished, consistent animation throughout GitLab.

See merge request !7780

Use :maximum instead of :within for length validators with a 0..N range

Closes #25209

See merge request !7894

Update php.md - /.dockerinit was removed in v1.11 so the test always results in …

See merge request !7882

Add excoveralls in list of coverage examples

See merge request !7906

Update custom_hooks.md for chained hooks support

See merge request !6721

Fix 404 error when visit group label edit page

Fixes https://gitlab.com/gitlab-org/gitlab-ce/issues/25158

See merge request !7957

Remove caching of Repository#has_visible_content?

This MR removes the caching of `Repository#has_visible_content?`. The cache for this method is no longer necessary and this should solve the problem described in https://gitlab.com/gitlab-org/gitlab-ce/issues/25278.

See merge request !7947

A simpler implementation of finding a merge request

## What does this MR do?

This cleans up some code in the issues API as discussed in https://gitlab.com/gitlab-org/gitlab-ce/merge_requests/7180#note_19501743

The helper method `merge_request_for_resolving_discussions` was no longer needed as it was only used once. That made it possible to simplify the implementation.

## Does this MR meet the acceptance criteria?

- [x] ~~[Changelog entry](https://docs.gitlab.com/ce/development/changelog.html) added~~
- [x] ~~[Documentation created/updated](https://gitlab.com/gitlab-org/gitlab-ce/blob/master/doc/development/doc_styleguide.md)~~
- [x] ~~API support added~~
- Tests
  - [x] Added for this feature/bug
  - [ ] All builds are passing
- [x] Conform by the [merge request performance guides](http://docs.gitlab.com/ce/development/merge_request_performance_guidelines.html)
- [x] Conform by the [style guides](https://gitlab.com/gitlab-org/gitlab-ce/blob/master/CONTRIBUTING.md#style-guides)
- [x] Branch has no merge conflicts with `master` (if it does - rebase it please)
- [x] [Squashed related commits together](https://git-scm.com/book/en/Git-Tools-Rewriting-History#Squashing-Commits)

## What are the relevant issue numbers?

!7180

See merge request !7955

Remove more pages css

* Moves award emojis to `/framework`
* Moves generic image styles to `/framework`
* Removes `confirmation.scss`

See merge request !7952

correct heading level for topics
Update puppet dev ops report for 2016

Remove dashboard.scss

See merge request !7960

# Conflicts:
#   app/assets/stylesheets/framework.scss

Remove tags.scss

Remove `tags.scss`

See merge request !7935

Remove admin.scss

Removes admin-specific CSS

See merge request !7932

https://gitlab.com/gitlab-org/gitlab-shell/merge_requests/93

https://gitlab.com/gitlab-org/gitlab-ce/issues/23036

https://gitlab.com/gitlab-org/gitlab-ce/issues/23036

Signed-off-by: Dmitriy Zaporozhets <dmitriy.zaporozhets@gmail.com>

Following a discussion in !7180

Encourage bug reporters to mention if they use GitLab.com [ci skip]

See merge request !7954

Explain "js: true" in "deleted_source_branch_spec.rb"

See merge request !7949