fix: add sanitize method to Granite model for tied embeddings (ml-explore#1298)

Author: SahilChachra

mlx_lm/models/granite.py

@@ -191,3 +191,8 @@ def __call__(
     @property
     def layers(self):
         return self.model.layers
+
+    def sanitize(self, weights):
+        if self.args.tie_word_embeddings:
+            weights.pop("lm_head.weight", None)
+        return weights