[CI] Remove Remaining Buildkite References in generate_test_report_lib
This patch removes the buildkite_info object from
generate_test_report_lib as we no longer support buildkite so it is dead
code now. Eventually we should set up equivalent functionality on the
Github side for downloading the logs from a convenient link, but for now
clean up the code.
Reviewers: cmtice, DavidSpickett, lnihlen
Reviewed By: DavidSpickett
Pull Request: https://github.com/llvm/llvm-project/pull/147784