entc/gen: delete removal edges from mutation (#1654)

* Remove Edge IDs from internal Mutation state

* Update template gen

* Update integration tests

* Update examples

examples/m2m2types/ent/mutation.go

@@ -188,6 +188,7 @@ func (m *GroupMutation) RemoveUserIDs(ids ...int) {
 		m.removedusers = make(map[int]struct{})
 	}
 	for i := range ids {
+		delete(m.users, ids[i])
 		m.removedusers[ids[i]] = struct{}{}
 	}
 }
@@ -625,6 +626,7 @@ func (m *UserMutation) RemoveGroupIDs(ids ...int) {
 		m.removedgroups = make(map[int]struct{})
 	}
 	for i := range ids {
+		delete(m.groups, ids[i])
 		m.removedgroups[ids[i]] = struct{}{}
 	}
 }