fix the lint error

Author: phuongdnguyen

temporal/datadog_checks/temporal/metrics.py

@@ -618,4 +618,4 @@
     'mutable_state_dirty': 'mutable_state.dirty',
     # History metrics
     'history_workflow_execution_cache_lock_hold_duration': 'history.workflow_execution_cache_lock_hold_duration',
-}
+}