[BUGFIX] Escape markup in Notification popups

Resolves: #71456
Releases: master
Change-Id: Iee2de13ed99192eabe010ee9c518e7726baa42f8
Reviewed-on: https://review.typo3.org/44658


Reviewed-by: Helmut Hummel <helmut.hummel@typo3.org>
Tested-by: Helmut Hummel <helmut.hummel@typo3.org>
Reviewed-by: Alexander Opitz <opitz.alexander@googlemail.com>
Tested-by: Alexander Opitz <opitz.alexander@googlemail.com>