Remove pyarrow dependency upper bound cap  

Pyarrow dependency has been capped at [<7](https://github.com/tensorflow/data-validation/blob/master/setup.py#L187). 

Is it possible to remove this cap? [The latest version of pyarrow is 11.0](https://pypi.org/project/pyarrow/). Removing this upper bound cap will allow folks to use TFDV with other frameworks. 

