[DOC] Typo in doc for In rule

[weber-s]

In the In rule, a copy/past typo from the Is rule:

https://github.com/daisylb/bridgekeeper/blob/d9ed685226e5b05d2a16f44390927932733b3728/bridgekeeper/rules.py#L484

Should read

    in_current_groups = In(lambda user: user.groups.all())