chore: remove @elmattic from Forest team

[LesnyRumcajs]

Summary

@elmattic who was removed in #177 got necromanced via d9b1f772. I think there's some issue with that sync bot but I'll just re-apply the patch again. Probably worth pinging whoever is maintaining the sync.

Why do you need this?

What else do we need to know?

DRI: myself

Reviewer's Checklist

• It is clear where the request is coming from (if unsure, ask)
• All the automated checks passed
• The YAML changes reflect the summary of the request
• The Terraform plan posted as a comment reflects the summary of the request

[github-actions]

The following access changes will be introduced as a result of applying the plan:

Access Changes

User elmattic:
  - will leave the organization
  - will lose push permission to builtin-actors
  - will lose push permission to f3-activation-contract
  - will lose push permission to fips
  - will lose push permission to fvm-test-vectors
  - will lose maintain permission to ref-fvm