Duplicate expand all files buttons
### Problem to solve
When I open a merge request where a file has been collapsed, a nice new warning banner is shown with an expand all files button ... but just above the warning banner is an expand all files button.
- why do I need two button?
- why not teach me where the button is normally so I learn where it is for other situations?

### Proposal
Remove button duplication and reduce the noise of the huge warning banner.
### Links / references
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issue