Fix commit SHA not showing in merge request compare dropdown

Closes #55822

See merge request gitlab-org/gitlab-ce!24084

Upgrade Omniauth and JWT gems to switch away from Google+ API

Closes #55668

See merge request gitlab-org/gitlab-ce!24068

Documentation process/policy updates to foster contributions to docs as SSOT

See merge request gitlab-org/gitlab-ce!23951

`--no-rdoc` and `--no-ri` have been deprecated since RubyGems 2.0:
https://github.com/rubygems/rubygems/blob/v2.0.0/History.txt#L43

They were finally removed in a recent release:
https://github.com/rubygems/rubygems/pull/2354

https://gitlab.com/gitlab-org/gitlab-ce/merge_requests/17011
in GitLab 11.1 refactored the merge request diff comparison
functionality but omitted the commit SHA due to a change in
the API (truncated_commit_sha -> short_commit_sha).

Closes https://gitlab.com/gitlab-org/gitlab-ce/issues/55822

Bump database_cleaner version

Closes #55539

See merge request gitlab-org/gitlab-ce!23985

Merge branch '52888-status-emoji-should-not-be-added-to-awards-section-on-issue-page-2' into 'master'

Resolve "Status emoji should not update awards section on issue page"

Closes #52888

See merge request gitlab-org/gitlab-ce!23470

Fixed content-disposition in blob and files API endpoint

Closes #55781

See merge request gitlab-org/gitlab-ce!24078

Stop using deprecated argument to `gem`

See merge request gitlab-org/gitlab-ce!24079

Add first-class releases API

See merge request gitlab-org/gitlab-ce!23795