[Task]: Update BigQueryIO.setTriggeringFrequency documentation

What needs to happen?

BigQueryIO currently documents triggering frequency as:

This is only applicable when the write method is set to {@link Method#FILE_LOADS}, and only when writing an unbounded {@link PCollection}.

However, we use triggering frequency for STORAGE_WRITE_API and STORAGE_API_AT_LEAST_ONCE as well. This documentation should be updated to reflect this.

In addition, during the validation component of BigQueryIO.write().expand(), we check for unbounded && (file loads || storage write api) to see if a triggering frequency is set. This should probably also be checked if storage write at least once is set.

Issue Priority

Priority: 2

Issue Component

Component: io-java-gcp