fix: fix buildkit config in ci

Signed-off-by: Adrien <adrien@huggingface.co>

.github/workflows/build.yaml

@@ -80,9 +80,7 @@ jobs:
         uses: docker/setup-buildx-action@v3
         with:
           install: true
-          buildkitd-config-inline: |
-            [registry."docker.io"]
-              mirrors = ["${{ env.REGISTRY_MIRROR }}"]
+          buildkitd-config: /tmp/buildkitd.toml
       - name: Login to internal Container Registry
         uses: docker/login-action@v3
         with: