[BUGFIX] Remove invalid attribute alt from textareas

The attribute alt is not allowed for the element "textarea".

Resolves: #92633
Releases: master, 10.4
Change-Id: I70790e529a270300f73d3b22cb598e2d8197e07c
Reviewed-on: https://review.typo3.org/c/Packages/TYPO3.CMS/+/66225


Tested-by: TYPO3com <noreply@typo3.com>
Tested-by: Daniel Haupt <mail@danielhaupt.de>
Tested-by: Michael Telgkamp <michael.telgkamp@mindscreen.de>
Tested-by: Markus Klein <markus.klein@typo3.org>
Tested-by: Oliver Bartsch <bo@cedev.de>
Tested-by: Daniel Goerz <daniel.goerz@posteo.de>
Reviewed-by: Daniel Haupt <mail@danielhaupt.de>
Reviewed-by: Josef Glatz <josefglatz@gmail.com>
Reviewed-by: Michael Telgkamp <michael.telgkamp@mindscreen.de>
Reviewed-by: Markus Klein <markus.klein@typo3.org>
Reviewed-by: Oliver Bartsch <bo@cedev.de>
Reviewed-by: Daniel Goerz <daniel.goerz@posteo.de>