Avoid deprecated ::set-output workflow command.

Signed-off-by: Anders Kaseorg <[email protected]>

Author: andersk

.github/workflows/local-test.yml

@@ -18,10 +18,8 @@ jobs:
         run: npm run package
       - name: Check whether integrations tests should be enabled
         id: enable_integration_tests
-        env:
-          ZULIP_API_KEY: ${{ secrets.ZULIP_API_KEY }}
         run: |
-          echo "::set-output name=value::${{ env.ZULIP_API_KEY != '' }}"
+          echo 'value=${{ secrets.ZULIP_API_KEY != '' }}' >> "$GITHUB_OUTPUT"
       - name: Send a stream message
         uses: ./send-message
         with: