[TASK] Remove option BE/notificationPrefix

The option is unused since 4.4

Resolves: #72615
Releases: master
Change-Id: Ie99b155f564a40532e5639726a8efc30eb4374ae
Reviewed-on: https://review.typo3.org/45797


Reviewed-by: Anja Leichsenring <aleichsenring@ab-softlab.de>
Tested-by: Anja Leichsenring <aleichsenring@ab-softlab.de>
Reviewed-by: Tymoteusz Motylewski <t.motylewski@gmail.com>
Reviewed-by: Michael Oehlhof <typo3@oehlhof.de>
Tested-by: Michael Oehlhof <typo3@oehlhof.de>
Reviewed-by: Markus Klein <markus.klein@typo3.org>
Tested-by: Markus Klein <markus.klein@typo3.org>