[CI] Fixed Deprecated save-output

save-output was deprecated. Resolved. See:
https://github.blog/changelog/2022-10-11-github-actions-deprecating-save-state-and-set-output-commands/

Author: AlexandreSinger

.github/workflows/containers.yml

@@ -36,7 +36,7 @@ jobs:
         id: generate
         run: |
           REPO='${{ github.repository }}'
-          echo "::set-output name=image::ghcr.io/${REPO,,}/ubuntu/focal/build"
+          echo "image=ghcr.io/${REPO,,}/ubuntu/focal/build" >> $GITHUB_OUTPUT
 
       - name: ⛴️ Build container image
         run: docker build -t ${{ steps.generate.outputs.image }} -f Dockerfile .