[AIRFLOW-6505] Let emoji encoded properly for json.dumps() -- BaseSQL…

…ToGoogleCloudStorageOperator

Make sure you have checked _all_ steps below.

### Jira

- [x] My PR addresses the following [Airflow Jira](https://issues.apache.org/jira/browse/AIRFLOW-6505) issues and references them in the PR title. For example, "\[AIRFLOW-XXX\] My Airflow PR"
  - https://issues.apache.org/jira/browse/AIRFLOW-6505

### Description
Emoji can't be encoded properly when ` json.dumps()` and 'UTF-8', problem fixed by adding parameter `ensure_ascii=False`. 
In line BaseSQLToGoogleCloudStorageOperato.

 

For example

the emoji 🍻 encoded differentially when in use or not use  `ensure_ascii=False`.

In Use (correct UTF-8 encode): "\xf0\x9f\x8d\xbb"

Not Use (only 2 slash):"\\\ud83c\\\udf7b"

 

Ref: https://stackoverflow.com/questions/51183947/python-json-dumps-doesnt-encode-emojis-properly



### Tests

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### Documentation

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  - If you implement backwards incompatible changes, please leave a note in the [Updating.md](https://github.com/apache/airflow/blob/master/UPDATING.md) so we can assign it to a appropriate release

### Code Quality

- [x] Passes `flake8`

airflow/contrib/operators/sql_to_gcs.py

@@ -177,7 +177,7 @@ def _write_local_data_files(self, cursor):
                 row_dict = dict(zip(schema, row))
 
                 # TODO validate that row isn't > 2MB. BQ enforces a hard row size of 2MB.
-                tmp_file_handle.write(json.dumps(row_dict, sort_keys=True).encode('utf-8'))
+                tmp_file_handle.write(json.dumps(row_dict, sort_keys=True, ensure_ascii=False).encode('utf-8'))
 
                 # Append newline to make dumps BigQuery compatible.
                 tmp_file_handle.write(b'\n')