fix push credentials for ghcr.io

Author: jcschaff

.github/workflows/docker.yml

@@ -22,8 +22,8 @@ jobs:
         uses: docker/login-action@v3
         with:
           registry: ghcr.io
-          username: ${{ secrets.ACTION_USER }}
-          password: ${{ secrets.ACTION_TOKEN }}
+          username: ${{ github.actor }}
+          password: ${{ secrets.GITHUB_TOKEN }}
 
       - name: Shorten SHA
         id: shorten_sha