Fix groupmap test for nsswitch changes (#13980)

Auto-generated winbind groups will no longer resolve into
unix groups when generating verbose groupmap output because
winbind is no longer by default in the nsswitch.conf due to
product improvements allowed by newer GCC in electric eel.

tests/api2/test_210_group.py

@@ -283,7 +283,7 @@ def test_27_full_groupmap_check(request):
         gid, sid = i
         entry = gm['builtins'][gid]
         assert entry['sid'] == sid, str(entry)
-        assert entry['unix_group'] == f'BUILTIN\\{entry["nt_name"].lower()}', str(entry)
+        assert entry['unix_group'] == gid, str(entry)
         assert entry['group_type_int'] == 4, str(entry)
         assert int(gid) == entry['gid'], str(entry)