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_init.py

@@ -4,6 +4,7 @@ import os
 import shutil
 from unittest.mock import patch, PropertyMock
 
+import pytest
 import requests
 
 import homeassistant.components.http as http
@@ -19,6 +20,14 @@ from tests.common import (
     mock_service)
 
 
+@pytest.fixture(autouse=True)
+def mutagen_mock():
+    """Mock writing tags."""
+    with patch('homeassistant.components.tts.SpeechManager.write_tags',
+               side_effect=lambda *args: args[1]):
+        yield
+
+
 class TestTTS(object):
     """Test the Google speech component."""