ci/check_secrets: Remove deprecated set-output

.github/workflows/ci.yml

@@ -146,17 +146,17 @@ jobs:
   check_secrets:
     permissions:
       contents: none
-    name: Check Docker secrets present for installer tests
+    name: Check presence of secrets
     runs-on: ubuntu-24.04
     outputs:
       docker: ${{ steps.secret.outputs.docker }}
     steps:
-      - name: Check for secrets
+      - name: Check for DockerHub secrets
         id: secret
         env:
           _DOCKER_SECRETS: ${{ secrets.DOCKERHUB_USERNAME }}${{ secrets.DOCKERHUB_TOKEN }}
         run: |
-          echo "::set-output name=docker::${{ env._DOCKER_SECRETS != '' }}"
+          echo "docker=${{ env._DOCKER_SECRETS != '' }}" >> $GITHUB_OUTPUT
 
   docker_push_image:
     needs: [tests, vm_tests, check_secrets]