Remove more test requirements (#7574)

* No longer require pyunify during tests

* No longer require cast during tests

* No longer required dependency for tests

* No longer require pymochad for tests

* Astral is a core dependency

* Avoid having to install datadog dependency during tests

* CMUS test doesn't test anything

* Frontier Silicon doesn't test anything

* No longer require mutagen

* Update requirements_test_all.txt

* Remove stale comment

tests/components/tts/test_voicerss.py

@@ -11,6 +11,8 @@ from homeassistant.setup import setup_component
 from tests.common import (
     get_test_home_assistant, assert_setup_component, mock_service)
 
+from .test_init import mutagen_mock  # noqa
+
 
 class TestTTSVoiceRSSPlatform(object):
     """Test the voicerss speech component."""