Use built-in test helpers on 3.8 (#34901)

tests/components/lovelace/test_resources.py

@@ -2,11 +2,11 @@
 import copy
 import uuid
 
-from asynctest import patch
-
 from homeassistant.components.lovelace import dashboard, resources
 from homeassistant.setup import async_setup_component
 
+from tests.async_mock import patch
+
 RESOURCE_EXAMPLES = [
     {"type": "js", "url": "/local/bla.js"},
     {"type": "css", "url": "/local/bla.css"},