[BUGFIX] Allow newlines in ConfirmationFinisher message

The ConfirmationFinisher in ext:form allows for adding messages with
a textarea. These are saved with newlines in YAML, but the Confirmation
partial never processed these newlines as <br> tags.

Resolves: #90244
Releases: master, 9.5
Change-Id: I80a9a73e83d122be47b61cb28b628479c5a8e43d
Reviewed-on: https://review.typo3.org/c/Packages/TYPO3.CMS/+/63505


Tested-by: TYPO3com <noreply@typo3.com>
Tested-by: Susanne Moog <look@susi.dev>
Tested-by: Daniel Goerz <daniel.goerz@posteo.de>
Reviewed-by: Oliver Bartsch <bo@cedev.de>
Reviewed-by: Andreas Fernandez <a.fernandez@scripting-base.de>
Reviewed-by: Guido Schmechel <guido.schmechel@brandung.de>
Reviewed-by: Susanne Moog <look@susi.dev>
Reviewed-by: Daniel Goerz <daniel.goerz@posteo.de>