Label www-gitlab-com contractor contributions

What does this MR do and why?

In a recent slack conversation @mxiao-ext noticed his www-gitlab-com project merge requests were getting labelled as community contributions.

It turns out our contractor labeller only runs for gitlab-org and we have a dedicated label policy for the www project.

This MR tweaks that policy to differenciate community and contractor contributions and label appropriately.

Expected impact & dry-runs

https://gitlab.com/gitlab-org/quality/triage-ops/-/jobs/6513266974

Action items

• If adding environment variables for reactive processors, update config/triage-web.yaml and .gitlab/ci/triage-web.yml
• (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