refactor: Remove unused imports and add exception comments

Co-authored-by: jmiller-moko <230051081+jmiller-moko@users.noreply.github.com>

scripts/maintenance/update_changelog.py

@@ -27,10 +27,8 @@ NOTE: Follows Keep a Changelog format, supports Added/Changed/Deprecated/Removed
 """
 
 import argparse
-import os
 import re
 import sys
-from datetime import datetime
 from pathlib import Path
 from typing import List, Optional