prevent dropdowns from being cut-off by scrollable tab container

What does this MR do?

#10775 set overflow: hidden on .scrollable-tabs-container (and a duplicate unneeded one). This limits it just to the the MR tabs

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

Is it better to fix markup/layout of the other scrollable tabs that this affects? Or fix them case-by-case (some might be better with collapsed/full width buttons etc)

Screenshots (if relevant)

Project dropdown works again, tab/button layout same as before the issue:

Resolve Discussions/tabs on MR still do what they should

Does this MR meet the acceptance criteria?

• Changelog entry added, if necessary
• [ ] 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 #32326 (closed)