Diffs should never be collapsed in the MR file-by-file view

Summary

Using file-by-file mode I expect no file to be collapsed by default. Using file-by-file mode signals the intent to review each file and there's no advantage to have any file collapsed when it's the only file displayed on the "page".

Steps to reproduce

Open an MR with a file that has a lot of changes (I don't know the exact threshold sorry!)

Example Project

gitlab-org/release/docs!215 (diffs)

What is the current bug behavior?

Diff is collapsed and requires click to be displayed.

What is the expected correct behavior?

Diff should be displayed

Relevant logs and/or screenshots

Output of checks

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Results of GitLab environment info

This happens on gitlab.com.

Results of GitLab application Check

This happens on gitlab.com.

Possible fixes

(If you can, link to the line of code that might be responsible for the problem)