Added group by on pull-request page

enables group pull request  by user or repo

Rollback Plan
-------------
* To roll back this change, revert the merge with: `git revert -m 1 MERGE_SHA` and perform another deploy.

URLs
----
> Links to bug tickets or user stories.

QA Plan
-------
> Fill in scenarios below. Review [QA Best Practices](https://source.sportngin.com/page/show/1227795-qa-best-practices).