Flickering note when changing tabs

Summary

Note (comment) flickers when it was loaded with AJAX and we changed tabs.

Steps to reproduce

1. Create an issue
2. Assign it to yourself
3. Switch to a different tab
4. Go back to the tab with the issue - system note about the assignment should appear
5. Switch to a different tab
6. Go back to the tab with the issue and observe the note - it flickers

This happens on dev.gitlab.com, but not on gitlab.com right now.

/cc @MadLittleMods

assigned to @MadLittleMods

mentioned in commit 08edfb67

mentioned in merge request !11281 (merged)

closed via merge request !11281 (merged)

mentioned in commit dinsaw/gitlab-ce@4067dd4f

changed milestone to %9.2

mentioned in commit 05886b93

mentioned in commit accdca5f

mentioned in commit nick.thomas/gitlab-ee@cc572c43

mentioned in merge request !14785