fix(PyMuPDF): store the str path instead of the Path object

llama_hub/file/pymu_pdf/base.py

@@ -1,4 +1,5 @@
 """Read PDF files using PyMuPDF library."""
+
 from pathlib import Path
 from typing import Dict, List, Optional, Union
 
@@ -57,7 +58,7 @@ def load(
             if not extra_info:
                 extra_info = {}
             extra_info["total_pages"] = len(doc)
-            extra_info["file_path"] = file_path
+            extra_info["file_path"] = str(file_path)
 
             # return list of documents
             return [