Remove accounts service remainders from ocs

- proxy routes everything user/group related (except of `user/signing-key`)
  to the reva ocs endpoint now
- remove the unused user and group methods from ocs

extensions/proxy/pkg/config/defaults/defaultconfig.go

@@ -85,7 +85,7 @@ func DefaultPolicies() []config.Policy {
 				},
 				{
 					Type:     config.RegexRoute,
-					Endpoint: "/ocs/v[12].php/cloud/(users?|groups)", // we have `user`, `users` and `groups` in ocis-ocs
+					Endpoint: "/ocs/v[12].php/cloud/user/signing-key", // only `user/signing-key` is left in ocis-ocs
 					Backend:  "http://localhost:9110",
 				},
 				{