[google sheets] mark batch_size and batch_bytes are non-required field

[varadarajan-tw]

Marks batch_size and batch_bytes as non-required fields. There are default values for these two fields even if the value is remain unset. So, it doesn't make sense to have these two are required fields.

Testing

• [ ] Added unit tests for new functionality
• [ ] Tested end-to-end using the local server
• [ ] [Segmenters] Tested in the staging environment