[AIRFLOW-2025] Reduced Logging verbosity

Closes apache#2967 from
britishbadger/reduce_logging_verbosity

airflow/contrib/operators/gcs_download_operator.py

@@ -75,4 +75,4 @@ def execute(self, context):
                 context['ti'].xcom_push(key=self.store_to_xcom_key, value=file_bytes)
             else:
                 raise RuntimeError('The size of the downloaded file is too large to push to XCom!')
-        self.log.info(file_bytes)
+        self.log.debug(file_bytes)