Fix the kernel-builder link

Author: danieldk

README.md

@@ -1,17 +1,16 @@
 # kernel-builder
 
-`kernel-builder` has moved to the [kernels](https://github.com/huggingface/kernels/tree/main/builder)
-repository. If you maintain any kernels, please update your `flake.nix`
-from
-
-```nix
-kernel-builder.url = "github:huggingface/kernel-builder";
-```
-
-to
-
-```nix
-kernel-builder.url = "github:huggingface/kernels";
-```
-
-and run `nix flake update` to update `flake.lock`.
+> [!IMPORTANT]
+> `kernel-builder` has moved to the [kernels](https://github.com/huggingface/kernels/) repository. If you maintain any kernels, please update your `flake.nix` from
+>
+> ```nix
+> kernel-builder.url = "github:huggingface/kernel-builder";
+> ```
+>
+> to
+>
+> ```nix
+> kernel-builder.url = "github:huggingface/kernels";
+> ```
+>
+> and run `nix flake update` to update `flake.lock`.