Fix failing static check (#16162)

This check was failing on master, example: https://github.com/apache/airflow/runs/2702121768#step:10:160

docs/apache-airflow/concepts/tasks.rst

@@ -135,7 +135,7 @@ is periodically executed and rescheduled until it succeeds.
 
     sensor = SFTPSensor(
         task_id="sensor",
-        path='/root/test',
+        path="/root/test",
         execution_timeout=timedelta(seconds=60),
         timeout=3600,
         retries=2,