[BUGFIX] Correct toolbar dropdown height

Ensure toolbar dropdowns are fully visible if space is available.

Resolves: #99862
Releases: main
Change-Id: I05272f6a02fa5fd3e808753d47c46cfdb66663b6
Reviewed-on: https://review.typo3.org/c/Packages/TYPO3.CMS/+/77736


Tested-by: core-ci <typo3@b13.com>
Tested-by: Benni Mack <benni@typo3.org>
Reviewed-by: Andreas Fernandez <a.fernandez@scripting-base.de>
Reviewed-by: Benni Mack <benni@typo3.org>
Tested-by: Andreas Fernandez <a.fernandez@scripting-base.de>