Fixes long commit messages overflow viewport in file tree

What does this MR do?

Fixes long commit messages breaking the table. It adds back a max-width in pixels instead of %.

Are there points in the code the reviewer needs to double check?

No.

Why was this MR needed?

To fix the overflow of the commit message

Screenshots (if relevant)

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 you do - rebase it please)
• Squashed related commits together

What are the relevant issue numbers?

Fixes #22544 (closed)