[BUGFIX] PHP Warning DBAL

[BUGFIX] PHP Warning DBAL

This patch fix the declaration of
TYPO3\CMS\Dbal\RecordList\DatabaseRecordList::makeSearchString
to be compatible with the parent method:
TYPO3\CMS\Recordlist\RecordList\AbstractDatabaseRecordList::makeSearchString

Resolves: #72912
Releases: master, 7.6
Change-Id: I313a35d9b2cc365b2d6012996551fb2ecb1ebbb0
Reviewed-on: https://review.typo3.org/46213
Reviewed-by: Wouter Wolters <typo3@wouterwolters.nl>
Reviewed-by: Andreas Fernandez <typo3@scripting-base.de>
Tested-by: Andreas Fernandez <typo3@scripting-base.de>
Reviewed-by: Morton Jonuschat <m.jonuschat@mojocode.de>
Tested-by: Morton Jonuschat <m.jonuschat@mojocode.de>
(cherry picked from commit c0a792d8e662d1f9a983408dec8b5c6307d8c706)
Reviewed-on: https://review.typo3.org/46219