Fix precommit hook to extract commit hash from nightly commit title instead of using the nightly commit hash

As titled.

Author: larryliu0820

.github/scripts/update_pytorch_pin.py

@@ -4,7 +4,6 @@
 import re
 import sys
 import urllib.request
-from datetime import datetime
 
 
 def parse_nightly_version(nightly_version):
@@ -75,13 +74,20 @@ def get_commit_hash_for_nightly(date_str):
         # Check if the first line of commit message matches
         first_line = commit_msg.split("\n")[0].strip()
         if first_line == target_title or first_line.startswith(f"{date_str} nightly"):
-            return commit["sha"]
+            return extract_hash_from_title(first_line)
 
     raise ValueError(
         f"Could not find commit with title matching '{target_title}' in nightly branch"
     )
 
 
+def extract_hash_from_title(title):
+    match = re.search(r"\(([0-9a-fA-F]{7,40})\)", title)
+    if not match:
+        raise ValueError(f"Could not extract commit hash from title '{title}'")
+    return match.group(1)
+
+
 def update_pytorch_pin(commit_hash):
     """
     Update .ci/docker/ci_commit_pins/pytorch.txt with the new commit hash.