Use Docker images from GitHub Container Registry

This isn't mandatory, but it's part of makedeb's change of source for Docker images from ProGet to the GitHub Container Registry.

It looks like the old images are also acting up, so this should help alleviate that.

.github/workflows/build-pkg.yml

@@ -72,7 +72,7 @@ jobs:
             -i \
             -v "${PWD}:/home/makedeb" \
             --platform "linux/${{ matrix.target.arch }}" \
-            "proget.${{ vars.HW_URL }}/docker/makedeb/makedeb:${{ matrix.target.image-tag }}"
+            "ghcr.io/makedeb/makedeb:${{ matrix.target.image-tag }}"
         env:
           SCRIPT: |
             export "DEBIAN_FRONTEND=${{ vars.DEBIAN_FRONTEND }}"
@@ -187,4 +187,4 @@ jobs:
         uses: actions/upload-artifact@v3
         with:
           name: "${{ matrix.target.distro }}-${{ matrix.target.display-arch }}"
-          path: 'pkg/*.deb'
+          path: 'pkg/*.deb'