update_time defined twice hence removing once. (#301)

Author: PandasPirate

google/generativeai/types/file_types.py

@@ -58,10 +58,6 @@ def update_time(self) -> datetime.datetime:
     def expiration_time(self) -> datetime.datetime:
         return self._proto.expiration_time
 
-    @property
-    def update_time(self) -> datetime.datetime:
-        return self._proto.update_time
-
     @property
     def sha256_hash(self) -> bytes:
         return self._proto.sha256_hash