Resolve "Buttons on new file page wrap outside of container for long branch names" - EE

What does this MR do?

EE port from: https://gitlab.com/gitlab-org/gitlab-ce/merge_requests/21015

Does this MR meet the acceptance criteria?

• Changelog entry added, if necessary
• Tests added for this feature/bug
• Conforms to the code review guidelines
  • Has been reviewed by a UX Designer
  • Has been reviewed by a Frontend maintainer
• EE specific content should be in the top level /ee folder
• Conforms to the merge request performance guidelines
• Conforms to the style guides
• Conforms to the database guides
• If you have multiple commits, please combine them into a few logically organized commits by squashing them

What are the relevant issue numbers?

https://gitlab.com/gitlab-org/gitlab-ce/issues/47752