Fix failing tests when G_MESSAGES_DEBUG is set (again)

Similar issue was fixed with commit f929d148, but it's happening again.
Define G_MESSAGES_DEBUG=all when running CI to ensure we won't regress
anymore.

gio/tests/gdbus-unix-addresses.c

@@ -128,6 +128,7 @@ test_x11_autolaunch (void)
       g_unsetenv ("DISPLAY");
       g_unsetenv ("DBUS_SESSION_BUS_ADDRESS");
       g_unsetenv ("XDG_RUNTIME_DIR");
+      g_unsetenv ("G_MESSAGES_DEBUG");
       set_up_mock_dbus_launch ();
 
       print_address ();