[!!!][TASK] Remove deprecated isLocalconfWritable function

Resolves: #61802
Releases: master
Change-Id: Iaa0b8a546b33b2c919987e12f684c356a9dfdf67
Reviewed-on: http://review.typo3.org/32927
Reviewed-by: Markus Klein <klein.t3@reelworx.at>
Tested-by: Markus Klein <klein.t3@reelworx.at>
Reviewed-by: Christian Kuhn <lolli@schwarzbu.ch>
Tested-by: Christian Kuhn <lolli@schwarzbu.ch>