Remove JUnit Report Feature Flag
## Overview In this epic work will be done to remove the feature flag for the [JUnit reports feature](https://docs.gitlab.com/ee/ci/junit_test_reports.html#enabling-the-feature). In order to do this we need to improve the performance of loading the test data on the tab. In current tests the tab loads in ~50 seconds for the gitlab.org project. Our target condition is to load that tab in ~20 seconds or less. Once we meet this condition the issue to remove the feature flag will be completed.
epic