[BUGFIX] Fix system maintainer access

Fix a check to not allow acces to admin users
but system maintainers only.

Change-Id: I2e5209bbaf7c3e3cee013d1fa08f48ff7e776956
Resolves: #82396
Related: #82306
Related: #82395
Releases: master
Reviewed-on: https://review.typo3.org/53965


Tested-by: TYPO3com <no-reply@typo3.com>
Reviewed-by: Benni Mack <benni@typo3.org>
Tested-by: Benni Mack <benni@typo3.org>
Reviewed-by: Anja Leichsenring <aleichsenring@ab-softlab.de>
Tested-by: Anja Leichsenring <aleichsenring@ab-softlab.de>
Reviewed-by: Christian Kuhn <lolli@schwarzbu.ch>
Tested-by: Christian Kuhn <lolli@schwarzbu.ch>