Closes#11400
Overflow is handled by javascript to show a button instead of horizontally scrolling, this is not the case when javascript is disabled. Add CSS to handle overflow, does not interfere with the javascript.
## Testing
1. Go to any repository.
2. Turn off javascript.
3. Make viewport width small.
4. Observe that repository menu under the repository header doesn't overflow.
Reviewed-on: https://codeberg.org/forgejo/forgejo/pulls/11614
Reviewed-by: 0ko <0ko@noreply.codeberg.org>
Reviewed-by: Beowulf <beowulf@beocode.eu>
Co-authored-by: Artyom Bologov <git@aartaka.me>
Co-committed-by: Artyom Bologov <git@aartaka.me>
