SKIP LOCKED only supported on MariaDB >=10.6

[life-style-de]

with version 2.2.0 the getUnhandledIndexQueueEntries in the IndexQueueRepository uses a query with SKIP LOCKED. SKIP LOCKED is only supported on MariaDB >=10.6 (https://mariadb.com/docs/server/reference/sql-statements/data-manipulation/selecting-data/select#skip-locked) (https://github.com/pimcore/generic-data-index-bundle/blob/2.x/src/Repository/IndexQueueRepository.php#L88-L106).

Pimcore currently still states to support MariaDB >= 10.3 (https://github.com/pimcore/pimcore/blob/12.x/doc/23_Installation_and_Upgrade/01_System_Requirements.md?plain=1#L50)

this change implicitly breaks this support. either the system requirements for Pimcore need to be updated or usage of SKIP LOCKED needs to be removed (replaced with an alternative).