[!!!][TASK] Remove global option "IPmaskMountGroups"

The option "IPmaskMountGroups" allows to automatically assign
usergroups to website visitors based on their incoming IP address / subnet.

This feature is useful for intranets, but very limited in its functionality
(e.g. auto-login for intranets is not possible, logging in from home with the
same user does not show the information), where it is recommended
to use more powerful third-party extensions instead.

Resolves: #91974
Releases: master
Change-Id: Idf219ba44242d37aca5212c50819aba964236a5f
Reviewed-on: https://review.typo3.org/c/Packages/TYPO3.CMS/+/65274


Tested-by: TYPO3com <noreply@typo3.com>
Tested-by: Christian Kuhn <lolli@schwarzbu.ch>
Tested-by: Andreas Fernandez <a.fernandez@scripting-base.de>
Reviewed-by: Christian Kuhn <lolli@schwarzbu.ch>
Reviewed-by: Andreas Fernandez <a.fernandez@scripting-base.de>