Group deletion should delete shares

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Steps to reproduce

1. create a folder "test"
2. create a group "test"
3. share folder "test" with group "test"
4. delete group test

Expected behaviour

delete shares of group if group get deleted.
if later same group name get created again (maybe with other members) it will automatically have all the shares from the past
(this is also a "security" topic)

Server configuration

Nextcloud version: 21.0.1