convery.py : fix Enum to IntEnum

Author: ggerganov

convert.py

@@ -72,7 +72,7 @@ class UnquantizedDataType:
 # TODO: match this with `llama_ftype`
 # TODO: rename to LLAMAFileType
 # TODO: move to `gguf.py`
-class GGMLFileType(enum.Enum):
+class GGMLFileType(enum.IntEnum):
     AllF32    = 0
     MostlyF16 = 1  # except 1d tensors