[BUGFIX] Move TCA modification of EXT:csc to TCA/Overrides

TCA manipulation code must no longer reside in ext_tables.php, but
moved to Configuration/TCA/Overrides/<tablename>.php. Leftovers
in ext_tables might disturb loading order of TCA changes and spoil
proper caching.

Change-Id: I3a357ddff0fe5d6f16caa67b4085372c27594234
Resolves: #59465
Related: #59414
Releases: 6.3, 6.2
Reviewed-on: https://review.typo3.org/31339
Reviewed-by: Wouter Wolters
Tested-by: Wouter Wolters