Use correct variables

.forgejo/workflows/docker-image.yaml

@@ -20,12 +20,12 @@ jobs:
         name: Set up Docker Buildx
         uses: docker/setup-buildx-action@v3
       -
-        name: Login to Docker Hub
+        name: Login to Container Registry
         uses: docker/login-action@v3
         with:
           registry: git.hamburg.ccc.de
-          username: ${{ secrets.FORGEJO_REGISTRY_USERNAME }}
-          password: ${{ secrets.FORGEJO_REGISTRY_TOKEN }}
+          username: ${{ secrets.REGISTRY_USERNAME }}
+          password: ${{ secrets.REGISTRY_TOKEN }}
       -
         name: Build and push
         uses: docker/build-push-action@v5