Disable Zulip part in GitHub Actions

Author: hewzhew

.github/workflows/build.yml

@@ -39,4 +39,4 @@ jobs:
           DEPLOY_GITHUB_USER: leanprover-community-bot
           github_repo: ${{ github.repository }}
           github_ref: ${{ github.ref  }}
-          ZULIP_KEY: ${{ secrets.ZULIP_KEY }}
+          # ZULIP_KEY: ${{ secrets.ZULIP_KEY }}