[BUGFIX] EXT:form - fix usage of deprecated functions

Resolves: #80987
Releases: master
Change-Id: Ib6d07021bc6784f74da135487c416af2f21cbd6b
Reviewed-on: https://review.typo3.org/52568


Tested-by: TYPO3com <no-reply@typo3.com>
Reviewed-by: Wouter Wolters <typo3@wouterwolters.nl>
Tested-by: Wouter Wolters <typo3@wouterwolters.nl>
Reviewed-by: Stefan Neufeind <typo3.neufeind@speedpartner.de>
Tested-by: Stefan Neufeind <typo3.neufeind@speedpartner.de>
Reviewed-by: Sascha Egerer <sascha@sascha-egerer.de>
Tested-by: Sascha Egerer <sascha@sascha-egerer.de>