Responsive title in diffs inline, side by side, with and without sidebar

What does this MR do?

Fixes the broken test so we can merge this again.

Original MR was reverted because it was breaking the tests, this is the original MR description:

What does this MR do?

Makes the file name in MR diffs responsive when:

• Diff is side by side and the sidebar is closed
• Diff is inline and the sidebar is closed
• Diff is side by side and the sidebar is opened
• Diff is inline and the sidebar is opened

Screenshots

Does this MR meet the acceptance criteria?

• Changelog entry added
• Documentation created/updated
• API support added
• Tests
  • Added for this feature/bug
  • All builds are passing
• Conform by the merge request performance guides
• Conform by the style guides
• Branch has no merge conflicts with master (if it does - rebase it please)
• Squashed related commits together

What are the relevant issue numbers?

Closes #25709 (closed)