chore: remove otto-review-gate workflow

[agentotto]

Removing the otto-review-gate.yml workflow as it is no longer needed.

---

Note

Medium Risk
Removes a security/compliance GitHub Actions check that enforced the Otto PR self-review gate, which could allow PRs to merge without that previously-required status check if not replaced elsewhere.

Overview
Removes the .github/workflows/otto-review-gate.yml GitHub Actions workflow that ran on pull_request_target/review events to set a status via worldcoin/gh-actions-public/otto-review-gate.

After this change, the repo will no longer publish the Otto review-gate status for PRs, so any branch protections or security controls depending on it must be updated accordingly.

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