bigquery: remove [Beta] from createQueryArrowStream at GA #9696

createQueryArrowStream() and its types are marked [Beta] / @beta. The backend currently marks the feature "This feature is not yet available" (QueryRequest.queryResultsFormat and ArrowSerializationOptions in the REST discovery document, ReadRowsRequest.arrow_serialization_options in storage.proto).

When the feature goes GA, remove [Beta] and @beta from:

• createQueryArrowStream() in handwritten/bigquery/src/bigquery.ts, along with the paragraph saying the ARROW format isn't generally available yet
• ArrowRecordBatchStream, ArrowQuery, and ArrowSerializationOptions in handwritten/bigquery/src/arrow.ts

ArrowSerializationOptions also passes picosTimestampPrecision through, so check that picosecond timestamps have launched before dropping @beta from it.

Python tracks the same cleanup in googleapis/google-cloud-python#18803.