Delete etl-graph job

[whd]

mozilla/telemetry-airflow#1567

CI is failing but I'm not sure if that's related to this change.

Checklist for reviewer:

• Commits should reference a bug or github issue, if relevant (if a bug is
  referenced, the pull request should include the bug number in the title)
• Scan the PR and verify that no changes (particularly to
  .circleci/config.yml) will cause environment variables (particularly
  credentials) to be exposed in test logs
• Ensure the container image will be using permissions granted to
  telemetry-airflow
  responsibly.

[scholtzan]

I think the failures might be related to some out-of-date dependencies. Don't think these changes have anything to do with them

[whd]

I manually pinned the broken dep ala aws/aws-sam-cli#3661 (comment) to get CI to pass.