Fix clicking of find and download areas on file page

What does this MR do?

Fixes the stacking context of the file page so the find and download areas can be clicked

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

Ney

Why was this MR needed?

We wanna click them. :(

What are the relevant issue numbers?

Closes #18340 (closed).

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 style guides
• Branch has no merge conflicts with master (if you do - rebase it please)
• Squashed related commits together