[BUGFIX] Fix #modulemenu collapsed state on Firefox

This fixes cut modulemenu icons on Firefox when scrollbars are shown.
It has been fixed before, but since then seemingly unrelated changes had
the problem resurface.

This time we set a min-width: for these links to prevent them from
shrinking even if the #modulemenu around them decides to give some space
to the scrollbar.

Resolves: #95656
Resolves: #94146
Related: #94633
Releases: master
Change-Id: I610f62f7f4730250c554c81edac91d5f9b37bb98
Reviewed-on: https://review.typo3.org/c/Packages/TYPO3.CMS/+/71795


Tested-by: Anja Leichsenring <aleichsenring@ab-softlab.de>
Tested-by: core-ci <typo3@b13.com>
Tested-by: Christian Kuhn <lolli@schwarzbu.ch>
Reviewed-by: Anja Leichsenring <aleichsenring@ab-softlab.de>
Reviewed-by: Christian Kuhn <lolli@schwarzbu.ch>