Resolve "Failed to generate lazy_heat_map"

Remove direct instance variable access that failed because of change to SimpleDelegator.

Dry run on the failed scheduled job: https://gitlab.com/gitlab-org/quality/triage-ops/-/jobs/710841498

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

Closes #550 (closed)