Fix GHCR Username in Container Builder (#25301)

.github/workflows/build-containers.yml

@@ -54,7 +54,7 @@ jobs:
         uses: docker/login-action@v1
         with:
           registry: ghcr.io
-          username: spack
+          username: ${{ github.actor }}
           password: ${{ secrets.GITHUB_TOKEN }}
 
       - name: Set up QEMU