Grammar and spelling fixes (#16065)

tests/components/persistent_notification/test_init.py

@@ -9,7 +9,7 @@ class TestPersistentNotification:
     """Test persistent notification component."""
 
     def setup_method(self, method):
-        """Setup things to be run when tests are started."""
+        """Set up things to be run when tests are started."""
         self.hass = get_test_home_assistant()
         setup_component(self.hass, pn.DOMAIN, {})