[CLEANUP] Correct phpDoc of FrontendLoginController->getDisplayText Function

The parameter $stdWrapArray is definied as string in the phpDoc
annotation @param. Corrected this to array

Resolves: #62636
Releases: master, 6.2
Change-Id: Ie5b30878fec65f6102ae4afc0a2f24a2b791a356
Reviewed-on: http://review.typo3.org/33740
Reviewed-by: Wouter Wolters <typo3@wouterwolters.nl>
Tested-by: Wouter Wolters <typo3@wouterwolters.nl>