Draft: Replace unlabelled report with untriaged report

Summary

Triage reports for untriaged issues have been created for the past while in gitlab-org/quality/triage-reports before switching over from indexing unlabelled issues.

This report aims to cover:

• New community issues
• All other issues that do not meet the criteria for a triaged issue

Closes #422 (closed)

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 =>
  • Week-in-review