metadata-push-hook: correct association key
Fixes urbit/landscape#405
=/ role=(unit (unit role-tag))
(role-for-ship:grp group.update src.bowl)
=/ =metadatum:store
- (need (peek-metadatum:met %contacts group.update))
+ (need (peek-metadatum:met %groups group.update))
?~ role %.n
?^ u.role
?=(?(%admin %moderator) u.u.role)
