chore: remove elmattic from Forest and Filecoin project

[LesnyRumcajs]

Summary

@elmattic last day in Forest team is today, so I'm removing him as part of our offboarding checklist.

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