Increase max items per triager

What does this MR do and why?

Describe in detail what your merge request does and why.

Occasionally we have an influx of wider community merge requests (normally as a result of a hackathon).

This MR improves the community merge request triage report by adding a note to the unassigned section and allocating up to 4 items per triager (currently 2).

Expected impact & dry-runs

https://gitlab.com/gitlab-org/quality/triage-ops/-/jobs/5783085409

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