[TASK] Remove unused TYPO3_CONF_VARS['FE']['logfile_dir']

Resolves: #52786
Releases: 6.2
Change-Id: Ib30f60bfa1b673a815edfa241089447d951dfd24
Reviewed-on: https://review.typo3.org/24735
Reviewed-by: Wouter Wolters
Reviewed-by: Georg Ringer
Tested-by: Georg Ringer