fix: Use pre-generated token

.forgejo/workflows/test.yml

@@ -25,8 +25,8 @@ jobs:
         uses: docker/login-action@v3
         with:
           registry: git.hamburg.ccc.de
-          username: ${{ secrets.REGISTRY_USERNAME }}
-          password: ${{ secrets.REGISTRY_TOKEN }}
+          username: oauth2accesstoken
+          password: ${{ secrets.GITHUB_TOKEN }}
       
       - name: Push Docker image to Container Registry
         run: |