Cleanup mqtt PLATFORMS constant and CI-test platform filters (#112847)

tests/components/mqtt/test_siren.py

@@ -17,7 +17,6 @@ from homeassistant.const import (
     STATE_OFF,
     STATE_ON,
     STATE_UNKNOWN,
-    Platform,
 )
 from homeassistant.core import HomeAssistant
 
@@ -60,13 +59,6 @@ DEFAULT_CONFIG = {
 }
 
 
-@pytest.fixture(autouse=True)
-def siren_platform_only():
-    """Only setup the siren platform to speed up tests."""
-    with patch("homeassistant.components.mqtt.PLATFORMS", [Platform.SIREN]):
-        yield
-
-
 async def async_turn_on(
     hass: HomeAssistant,
     entity_id: str = ENTITY_MATCH_ALL,