[FOLLOWUP][TASK] Remove column sys_file_reference.sorting

Table sys_file_reference is used as "inline 1:n foreign_field" composite
assiciation and is processed in RelationHandler methods readForeignField
and writeForeignField. Albeit it looks like an MM table it still is a
regular TCA table being used as an entity with further attributes.

That's why this follow-up reverts the changes in file RelationHandler.php
that have been introduced in 728bfc19.

Related: #83160
Releases: master
Change-Id: I4b7a78a0ee494af9492996e81c2b631c29832cc6
Reviewed-on: https://review.typo3.org/55107


Tested-by: TYPO3com <no-reply@typo3.com>
Reviewed-by: Susanne Moog <susanne.moog@typo3.org>
Tested-by: Susanne Moog <susanne.moog@typo3.org>
Reviewed-by: Stephan Großberndt <stephan@grossberndt.de>
Reviewed-by: Oliver Hader <oliver.hader@typo3.org>
Tested-by: Oliver Hader <oliver.hader@typo3.org>