[TASK] Superfluous comparison in OpendocsController

Fix superfluous comparison against boolean in
OpendocsController::checkAccess

Change-Id: I0682042848f2f25856506d5949fc724853c43948
Resolves: #54052
Releases: 6.2
Reviewed-on: https://review.typo3.org/25739
Reviewed-by: Jo Hasenau
Reviewed-by: Michiel Roos
Tested-by: Michiel Roos
Reviewed-by: Markus Klein
Tested-by: Markus Klein