Small cleanup of MQTT mixins (#66812)

homeassistant/components/mqtt/mixins.py

@@ -839,12 +839,11 @@ def async_removed_from_device(
         if "config_entries" not in event.data["changes"]:
             return False
         device_registry = dr.async_get(hass)
-        device_entry = device_registry.async_get(mqtt_device_id)
+        device_entry = device_registry.async_get(device_id)
         if not device_entry:
             # The device is already removed, do cleanup when we get "remove" event
             return False
-        entry_id = config_entry_id
-        if entry_id in device_entry.config_entries:
+        if config_entry_id in device_entry.config_entries:
             # Not removed from device
             return False