ParquetIO throws Coder not found when using parseGenericRecord or parseFilesGenericRecord

ParquetIO is missing output coder  when  using a user-specified parsing function with `parseGenericRecord` or `parseFilesGenericRecord` feature for reading Parquet files with unknown schema.

Workaround:
Use `setCoder` directly on the output `PCollection`
for example:

SerializableFunction<GenericRecord, Foo> parseFn = ...;
Coder<Foo> fooCoder = ...;
PCollection<Foo> records = p.apply(ParquetIO.parseGenericRecords(parseFn).from(...))
.setCoder(fooCoder);