Update load test for GardenPAC heatpump for generic class.

When removing the gardenpac legacy class, the test for recognizing and loading
it was missed, leading to a failure.

tests/test_device_config.py

@@ -188,7 +188,7 @@ class TestDeviceConfig(unittest.TestCase):
         self._test_detect(
             GARDENPAC_HEATPUMP_PAYLOAD,
             CONF_TYPE_GARDENPAC_HEATPUMP,
-            "GardenPACPoolHeatpump",
+            None,
         )
 
     def test_purline_heater_detection(self):