Exclude qa and docs from Rails 4 builds

Closes #54059

See merge request gitlab-org/gitlab-ce!23091

Closes https://gitlab.com/gitlab-org/gitlab-ce/issues/54059

Fix bug causing not all emails to show up in commit email selectbox

Closes #54045

See merge request gitlab-org/gitlab-ce!23079

Fix styling of snippet and commit discussion comments

Closes #53918

See merge request gitlab-org/gitlab-ce!23035

Closes https://gitlab.com/gitlab-org/gitlab-ce/issues/54045

Fix vertical line alignment in discussion & diff border-radius

Closes #53975

See merge request gitlab-org/gitlab-ce!23075

Add white background to commit diff comments

See merge request gitlab-org/gitlab-ce!23078

Fix Git protocol v2 e2e test

Closes gitlab-org/quality/staging#16

See merge request gitlab-org/gitlab-ce!23067

Update proofreader.md

See merge request gitlab-org/gitlab-ce!20752

Updates pipeline code to use gitlab-ui

See merge request gitlab-org/gitlab-ce!22999

Remove references to `Factory`

Fix collapsed files not fully fully expanding

Closes #53866

See merge request gitlab-org/gitlab-ce!23019

Disable updating appearance of filter tokens for special values

Closes #53636

See merge request gitlab-org/gitlab-ce!22865

Add a new markup languages section

See merge request gitlab-org/gitlab-ce!22921

Show navigation line separator when instance metrics is disabled

See merge request gitlab-org/gitlab-ce!22940

Add missing slash in frontend testing guide

See merge request gitlab-org/gitlab-ce!23027

Switch to Rails 5

Closes #14286 and #48991

See merge request gitlab-org/gitlab-ce!21492

Move cloud-native-image to the post-test stage

Closes charts/gitlab#897

See merge request gitlab-org/gitlab-ce!22942

Bump GitLab Workhorse to 7.1.1

See merge request gitlab-org/gitlab-ce!23053

Bump `binding_of_caller` gem version to 0.8.0

See merge request gitlab-org/gitlab-ce!23040

Merge branch '54002-activity-feed-missing-padding-in-event-note-when-a-branch-is-deleted' into 'master'

Resolve "Activity Feed - Missing padding in event note when a branch is deleted"

Closes #54002

See merge request gitlab-org/gitlab-ce!23038

This version now supports redis[s]:// URL schemes.

In Rails 5 all models by default inherit from ApplicationRecord.

We want to run CI with rails 4 for a short-term (until we are sure that
we will ship with rails 5). The problem is that rails 4 can not handle
rails 5 schema.rb properly - specifically `t.index` directive can not
handle multiple indexes on the same column.

Because combination of rails 4 + rails 5 schema will be used
only in CI for a short-term, we can just ignore these incompatibility
failures. This patch adds `rails5` helper for specs.

* add_index replaced with t.index
* intiger(size 8) replaced with bigint