Clean up `group_member_inherited_group` feature flag

What does this MR do and why?

The group_member_inherited_group feature flag was introduced in !71465 (merged) and the feature flag will be rolled out in #357244 (closed) on 2022-06-09 at 16:00 UTC.

This MR cleans up the group_member_inherited_group feature flag.

🛠 with ❤ at Siemens

/cc @bufferoverflow

How to set up and validate locally

see !71465 (merged)

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