fix typo in comment (#318)

convert-pth-to-ggml.py

@@ -67,7 +67,7 @@ def write_header(fout, hparams, ftype):
 
     keys = ["vocab_size", "dim", "multiple_of", "n_heads", "n_layers"]
     values = [
-        0x67676d66,  # magic: ggml in hex
+        0x67676d66,  # magic: ggmf in hex
         1, # file version
         *[hparams[key] for key in keys],
         hparams["dim"] // hparams["n_heads"],  # rot (obsolete)