terraform: fix package maintainer team groups

Previously we have declared explicit resources for the roles under the
root. This lead to the desired groups getting created twice, once via
toSet of the package maintainer team and once per resource under the
root.

Furthermore remove the package maintainer roles, currently we do not
need any roles to define permissions. We can simply use the groups to
easily assign users into. Those group assignments can be queries for
example by gluebuddy to act upon or queried by a saml client.

Fixes 941563f2