Allow JSON type in TableSchema for WriteToBigQuery with FILE_LOAD method in Python SDK

[sapphire008]

Removing the JSON type check when using WriteToBigQuery with FILE_LOAD method in Python SDK. Throwing a warning instead.

• Related to the change in Java SDK: https://github.com/apache/beam/pull/29923. Consistent with this PR for Java SDK, I have changed the raise ValueError to a logging.warn`.
• Relevant lines of code https://github.com/apache/beam/blob/8a74a1c279c86a262def9b99418e7eb03366e2d9/sdks/python/apache_beam/io/gcp/bigquery.py#L2178-L2191

I did some hackish testing against a table of my own and it was able to insert the json fields correctly without a problem.

NOT RECOMMENDED but it solves the problem for those who need this tomorrow:

In my docker file that has Apache Beam installed, I used sed to replace the check:

RUN sed -i 's/if field\['\''type'\''\] == '\''JSON'\'':/if field\['\''type'\''\] == '\''JSON_IS_OKAY'\'':/g' /usr/local/lib/python3.11/site-packages/apache_beam/io/gcp/bigquery.py

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