[BE] remove unused RDS pipeline from print_test_stats.py (#77654)
Now that Grafana is deprecated and we report test status + flaky tests to Rockset, we should remove the need to write to RDS at all.
Some runners (like ROCm) don't have permissions to write to RDS on pull requests anyway so this was causing a split in stats.
Next steps:
- Remove RDS in binary_size and sccache stats.
Pull Request resolved: https://github.com/pytorch/pytorch/pull/77654
Approved by: https://github.com/mehtanirav, https://github.com/malfet, https://github.com/seemethere