Update type hint for prepare_comment argument

Replaces the use of the PEP 604 union operator (|) with typing.Union for compatibility. This change ensures the code works with Python versions prior to 3.10.

Author: karangattu

tests/inspect-ai/scripts/prepare_comment.py

@@ -2,9 +2,10 @@
 import json
 import sys
 from pathlib import Path
+from typing import Union
 
 
-def prepare_comment(summary_path: str | Path) -> int:
+def prepare_comment(summary_path: Union[str, Path]) -> int:
     """
     Reads summary.json and creates a formatted comment for GitHub PR.