Merge branch 'rails5-fix-47370' into 'master'

Use same gem versions for rails5 as for rails4 where possible

Closes #47370, #46232, #47367, and #47373

See merge request gitlab-org/gitlab-ce!19498

Gemfile.lock

@@ -452,7 +452,6 @@ GEM
     kgio (2.10.0)
     knapsack (1.16.0)
       rake
-      timecop (>= 0.1.0)
     kubeclient (3.1.0)
       http (~> 2.2.2)
       recursive-open-struct (~> 1.0, >= 1.0.4)

changelogs/unreleased/rails5-fix-47370.yml

+---
+title: Use same gem versions for rails5 as for rails4 where possible
+merge_request: 19498
+author: Jasper Maes
+type: fixed