ci/docker_push_image: Remove dead step

This step is now part of the check_secrets job and
the output is completely unused.

.github/workflows/ci.yml

@@ -169,12 +169,6 @@ jobs:
       github.ref_name == 'master'
     runs-on: ubuntu-24.04
     steps:
-    - name: Check for secrets
-      id: secret
-      env:
-        _DOCKER_SECRETS: ${{ secrets.DOCKERHUB_USERNAME }}${{ secrets.DOCKERHUB_TOKEN }}
-      run: |
-        echo "::set-output name=docker::${{ env._DOCKER_SECRETS != '' }}"
     - uses: actions/checkout@v5
       with:
         fetch-depth: 0