convert-hf : fix Refact conversion

Author: compilade

convert-hf-to-gguf.py

@@ -999,7 +999,7 @@ def modify_tensors(self, data_torch: Tensor, name: str, bid: int | None) -> Iter
         ff_dim = multiple_of * ((hidden_dim + multiple_of - 1) // multiple_of)
         n_head = self.hparams["n_head"]
         n_head_kv = 1
-        head_dim = hidden_dim // n_head
+        head_dim = self.hparams["n_embd"] // n_head
 
         tensors: list[tuple[str, Tensor]] = []