[BUGFIX] Do not use deprecated $R_URI

Resolves: #84649
Releases: master
Change-Id: I98ec184e4b2d15d04515ba121babb470ac832882
Reviewed-on: https://review.typo3.org/56606


Reviewed-by: Mathias Schreiber <mathias.schreiber@typo3.com>
Tested-by: Mathias Schreiber <mathias.schreiber@typo3.com>
Tested-by: TYPO3com <no-reply@typo3.com>
Reviewed-by: Benni Mack <benni@typo3.org>
Tested-by: Benni Mack <benni@typo3.org>