refactor(bigquery): remove hardcoded DATE/DATETIME/JSON, require type_overrides

Author: enzomaruffa

CHANGES.md

@@ -68,7 +68,7 @@
 
 ## New Features / Improvements
 
-* Added `type_overrides` parameter to `WriteToBigQuery` allowing users to specify custom BigQuery to Python type mappings when using Storage Write API (Python) ([#25946](https://github.com/apache/beam/issues/25946)).
+* Added `type_overrides` parameter to `WriteToBigQuery` allowing users to specify custom BigQuery to Python type mappings when using Storage Write API. This enables support for types like DATE, DATETIME, and JSON (Python) ([#25946](https://github.com/apache/beam/issues/25946)).
 
 ## Breaking Changes
 

sdks/python/apache_beam/io/gcp/bigquery_schema_tools.py

@@ -49,9 +49,6 @@
     "BYTES": bytes,
     "TIMESTAMP": apache_beam.utils.timestamp.Timestamp,
     "GEOGRAPHY": str,
-    "DATE": str,
-    "DATETIME": str,
-    "JSON": str,
     #TODO(https://github.com/apache/beam/issues/20810):
     # Finish mappings for all BQ types
 }