[BUGFIX] Fix broken additional fields for garbarge collection task

The new IpAnonymizationAdditionalFieldProvider introduced the same
JavaScript variable which breaks the garbage collection task.
The JavaScript initialization has been removed and the field provider 
simplified.

Resolves: #85068
Releases: master, 8.7, 7.6
Change-Id: Ibb307ee37d6fea33a721373bdc50bbbd3fee1453
Reviewed-on: https://review.typo3.org/57136


Tested-by: TYPO3com <no-reply@typo3.com>
Reviewed-by: Anja Leichsenring <aleichsenring@ab-softlab.de>
Tested-by: Anja Leichsenring <aleichsenring@ab-softlab.de>
Reviewed-by: Christian Kuhn <lolli@schwarzbu.ch>
Tested-by: Christian Kuhn <lolli@schwarzbu.ch>