[BUGFIX] Fix namespace in check extensionmanager list acceptance test

Resolves: #75628
Releases: master
Change-Id: I20bab4abea826e4e8cfb1b2a718f438ed22ccd72
Reviewed-on: https://review.typo3.org/47675


Reviewed-by: Wouter Wolters <typo3@wouterwolters.nl>
Reviewed-by: Sascha Egerer <sascha@sascha-egerer.de>
Tested-by: Sascha Egerer <sascha@sascha-egerer.de>