fix: recognize copilot-pull-request-reviewer in ci-gate

The Copilot review bot uses the login 'copilot-pull-request-reviewer',
which was not in the reviewer set. This caused the ci-gate to fail to
add the ready-for-ci label after Copilot review.

Co-authored-by: Copilot <223556219+Copilot@users.noreply.github.com>

Author: lpcox

.github/workflows/ci-gate.yml

@@ -25,7 +25,7 @@ jobs:
         uses: actions/github-script@v7
         with:
           script: |
-            const copilotReviewers = new Set(['copilot', 'copilot[bot]', 'Copilot']);
+            const copilotReviewers = new Set(['copilot', 'copilot[bot]', 'Copilot', 'copilot-pull-request-reviewer']);
             const isCopilotReviewer = login => copilotReviewers.has(login ?? '');
             const { owner, repo } = context.repo;
             const pr_number = context.payload.pull_request?.number