Merge branch 'forks_tooltip' into 'master'

Add tooltip to project fork count

## What does this MR do?

Adds a tooltip reading `Forks` when a user hovers over the count of project forks.

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

## Why was this MR needed?

Requested in #23066 

## Screenshots (if relevant)

![image](/uploads/023af8dc4df68549705f6a328cf8031c/image.png)

## Does this MR meet the acceptance criteria?

- [x] [CHANGELOG](https://gitlab.com/gitlab-org/gitlab-ce/blob/master/CHANGELOG) entry 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)
- [x] Branch has no merge conflicts with `master` (if you do - 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?

#23066

See merge request !6718

CHANGELOG

@@ -34,6 +34,7 @@ v 8.13.0 (unreleased)
   - Close open merge request without source project (Katarzyna Kobierska Ula Budziszewska)
   - Fix that manual jobs would no longer block jobs in the next stage. !6604
   - Add configurable email subject suffix (Fu Xu)
+  - Added tooltip to fork count on project show page. (Justin DiPierro)
   - Use a ConnectionPool for Rails.cache on Sidekiq servers
   - Replace `alias_method_chain` with `Module#prepend`
   - Enable GitLab Import/Export for non-admin users.

app/views/projects/buttons/_fork.html.haml

@@ -5,10 +5,10 @@
         = custom_icon('icon_fork')
         %span Fork
     - else
-      = link_to new_namespace_project_fork_path(@project.namespace, @project), title: "Fork project", class: 'btn has-tooltip' do
+      = link_to new_namespace_project_fork_path(@project.namespace, @project), title: 'Fork project', class: 'btn has-tooltip' do
         = custom_icon('icon_fork')
         %span Fork
     %div.count-with-arrow
       %span.arrow
-      = link_to namespace_project_forks_path(@project.namespace, @project), class: "count" do
+      = link_to namespace_project_forks_path(@project.namespace, @project), title: 'Forks', class: 'count has-tooltip' do
         = @project.forks_count