Merge request warning when some files are collapsed stays visible

Problem

The following discussion from !40752 (merged) should be addressed:

• @pedroms started a discussion: (+2 comments)

  @thomasrandolph 🐛 Bug: If you manually collapse a file before expanding an auto-collapsed file, the alert stays visible until you expand all files (even if they were initially collapsed by the user):

  CleanShot_2020-09-03_at_18.57.02

  In the video above, the file that is auto-collapsed on page load is package-lock.json.

Proposal

This issue should rely on the new approach to Differentiate between automatically collapsed and manually (user) collapsed diff files.