Fix the MPS RMSNorm hub kernel repo id (#50714)

Fix the MPS RMSNorm hub kernel repo id (mlx-rmsnorm)

Author: tarekziade

src/transformers/integrations/hub_kernels.py

@@ -491,7 +491,7 @@ def _build_kernel_mapping() -> dict:
                 },
                 "mps": {
                     Mode.INFERENCE: LayerRepository(
-                        repo_id="kernels-community/mlx_rmsnorm",
+                        repo_id="kernels-community/mlx-rmsnorm",
                         layer_name="RMSNorm",
                         version=1,
                     )