[BUGFIX] Keep RecordListController->modTSconfig public

For now, we have to keep property modTSconfig public in
RecordListController since it is used from DatabaseRecordList
via infamous $GLOBALS['SOBE'] and otherwise shows deprecation
notices in list module :(

Resolves: #85030
Related: #85016
Releases: master
Change-Id: I40bdd54a89e2282d8403b633fb08c505b214c338
Reviewed-on: https://review.typo3.org/56987


Tested-by: TYPO3com <no-reply@typo3.com>
Reviewed-by: Anja Leichsenring <aleichsenring@ab-softlab.de>
Tested-by: Anja Leichsenring <aleichsenring@ab-softlab.de>
Reviewed-by: Andreas Fernandez <a.fernandez@scripting-base.de>
Tested-by: Andreas Fernandez <a.fernandez@scripting-base.de>