[TASK] Add missing breaking rst for form setup mixins removal

Adds the forgotten breaking rst for the ticket
https://review.typo3.org/c/Packages/TYPO3.CMS/+/70528/

Resolves: #94911
Releases: master
Change-Id: I1a0e9c1b074b377febd655cc96a1a1033b56fc35
Reviewed-on: https://review.typo3.org/c/Packages/TYPO3.CMS/+/70652


Tested-by: Mathias Brodala <mbrodala@pagemachine.de>
Tested-by: core-ci <typo3@b13.com>
Tested-by: waldhacker <hello@waldhacker.dev>
Reviewed-by: Mathias Brodala <mbrodala@pagemachine.de>
Reviewed-by: waldhacker <hello@waldhacker.dev>