Use argument out_dir not self.out_dir

Author: nzw0301

pytorch_pfn_extras/writing/_writer_base.py

@@ -286,7 +286,6 @@ def save(
         append: bool,
         **savefun_kwargs: Any,
     ) -> None:
-        out_dir = self.out_dir
         if not self._initialized:
             self.initialize(out_dir)