[BUGFIX] Adapt datepicker styles

Currently, the year selector shows arrows which overlay the
css styles and the current day style is equal to the
selected day.

This has been changed by hiding the arrows for the
year selector and using disabled background color
for the current day (today).

Resolves: #100884
Releases: main, 12.4
Change-Id: I1f0e89e9fd5a59f90d97eb340b575d9c27a42718
Reviewed-on: https://review.typo3.org/c/Packages/TYPO3.CMS/+/79139


Tested-by: core-ci <typo3@b13.com>
Reviewed-by: Oliver Bartsch <bo@cedev.de>
Tested-by: Oliver Bartsch <bo@cedev.de>