Remove useless string split from mqtt diagnostics (#166035)

Author: emontnemery

homeassistant/components/mqtt/diagnostics.py

@@ -13,7 +13,7 @@
     CONF_PASSWORD,
     CONF_USERNAME,
 )
-from homeassistant.core import HomeAssistant, callback, split_entity_id
+from homeassistant.core import HomeAssistant, callback
 from homeassistant.helpers import device_registry as dr, entity_registry as er
 from homeassistant.helpers.device_registry import DeviceEntry
 
@@ -103,10 +103,8 @@ def _state_dict(entity_entry: er.RegistryEntry) -> dict[str, Any] | None:
         # The context doesn't provide useful information in this case.
         state_dict.pop("context", None)
 
-        entity_domain = split_entity_id(state.entity_id)[0]
-
         # Retract some sensitive state attributes
-        if entity_domain == device_tracker.DOMAIN:
+        if state.domain == device_tracker.DOMAIN:
             state_dict["attributes"] = async_redact_data(
                 state_dict["attributes"], REDACT_STATE_DEVICE_TRACKER
             )