[TASK] Remove left over refindex _FILE handling

ReferenceIndex does not write rows with
'ref_table' set to '_FILE' anymore since #87428.
The patch removes some left over handling at
a couple of places.

Resolves: #103710
Related: #87428
Related: #102222
Releases: main
Change-Id: Iccb94a57b7fb551da48ba516b668fe970b9fb5f4
Reviewed-on: https://review.typo3.org/c/Packages/TYPO3.CMS/+/84001


Tested-by: Jochen Roth <rothjochen@gmail.com>
Reviewed-by: Christian Kuhn <lolli@schwarzbu.ch>
Reviewed-by: Jochen Roth <rothjochen@gmail.com>
Tested-by: core-ci <typo3@b13.com>
Tested-by: Stefan Bürk <stefan@buerk.tech>
Reviewed-by: Stefan Bürk <stefan@buerk.tech>
Tested-by: Christian Kuhn <lolli@schwarzbu.ch>