Remove MONOREPO_READ_TOKEN — monorepo is public, no token needed

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

Author: edburns

.github/workflows/deploy-site.yml

@@ -67,7 +67,6 @@ jobs:
           repository: github/copilot-sdk
           ref: ${{ inputs.monorepo_tag }}
           path: monorepo
-          token: ${{ secrets.MONOREPO_READ_TOKEN }}
 
       # 3. Set up JDK
       - name: Set up JDK 25