Use ci-perf-kit 0.7.4: ignore runs with unmatched key/value in the logs.

[qinsoon]

The perf CI run for mutator performance recently failed for the following error:

++ python3 scripts/mutator_report.py /home/gitlab-runner/actions-runner/_work/mmtk-core/mmtk-core/ci-perf-kit/result_repo/mutator /home/gitlab-runner/actions-runner/_work/mmtk-core/mmtk-core/reports/master
Traceback (most recent call last):
  File "/home/gitlab-runner/actions-runner/_work/mmtk-core/mmtk-core/ci-perf-kit/scripts/mutator_report.py", line 43, in <module>
    run_id, results = parse.parse_run(os.path.join(result_repo_mutator_root, l))
  File "/home/gitlab-runner/actions-runner/_work/mmtk-core/mmtk-core/ci-perf-kit/scripts/parse.py", line 82, in parse_run
    results.append(parse_log(os.path.join(log_folder, l), n_invocations))
  File "/home/gitlab-runner/actions-runner/_work/mmtk-core/mmtk-core/ci-perf-kit/scripts/parse.py", line 48, in parse_log
    assert len(mmtk_keys) == len(mmtk_values), "Error when reading MMTk statistics: num of keys does not match num of values"
AssertionError: Error when reading MMTk statistics: num of keys does not match num of values

One of the runs recently has an incomplete MMTk Statistics printing. The process quit for some reason before it prints the values. This seems to be a random issue, as the other runs in the same log file look fine.

============================ MMTk Statistics Totals ============================
GC time.other time.stw time.jitc time.ygc collections.young time.ogc collections.old

The unmatched key/value pairs caused an assertion failure in the ci-perf-kit script.ci-perf-kit 0.7.4 (https://github.com/mmtk/ci-perf-kit/releases/tag/0.7.4) fixes this. Runs that do not have valid key/value pairs will be ignored, and the script will not quit.

[wks]

LGTM