[BUGFIX] Show "FlashMessage" finisher output

Resolves: #84699
Releases: master, 9.5
Change-Id: I2733556eae95db5f44867323cd217c4b3ea0127c
Reviewed-on: https://review.typo3.org/c/Packages/TYPO3.CMS/+/60576


Tested-by: TYPO3com <noreply@typo3.com>
Tested-by: Susanne Moog <look@susi.dev>
Tested-by: Ralf Zimmermann <ralf.zimmermann@tritum.de>
Reviewed-by: Björn Jacob <bjoern.jacob@tritum.de>
Reviewed-by: Susanne Moog <look@susi.dev>
Reviewed-by: Ralf Zimmermann <ralf.zimmermann@tritum.de>