Exclude `gitlab-qa` from being detected as community contributor

What does this MR do and why?

It was noticed by @jannik_lehmann that @gitlab-qa was detected as Community contribution (https://gitlab.com/gitlab-org/gitlab/-/merge_requests?author_username=gitlab-qa&scope=all&sort=created_asc&state=opened). It seems to have started 3 days ago, strangely. I think excluding @gitlab-qa as being a bot is the right call here?

Expected impact & dry-runs

These are strongly recommended to assist reviewers and reduce the time to merge your change.

See https://gitlab.com/gitlab-org/quality/triage-ops/-/tree/master/doc/scheduled#testing-with-a-dry-run on how to perform dry-runs.

Action items

• (If applicable) Add documentation to the handbook pages for Triage Operations =>
• (If applicable) Identify the affected groups and how to communicate to them:
  • /cc @person_or_group =>
  • Relevant Slack channels =>
  • Engineering week-in-review