fix(serializers): Remove sensitive data from serializer exception logging

Remove the exception object from logger extras to avoid logging sensitive
data (secrets, passwords) in cleartext, as flagged by CodeQL. The
exception traceback is still captured by logger.exception and
sentry_sdk.capture_exception.

Co-Authored-By: Claude Opus 4.6 <noreply@example.com>

Author: leeandher

src/sentry/api/serializers/base.py

@@ -118,7 +118,8 @@ def _serialize(
         try:
             return self.serialize(obj, attrs, user, **kwargs)
         except Exception as e:
-            logger.exception("Failed to serialize", extra={"instance": obj, "exception": e})
+            logger.exception("Failed to serialize", extra={"instance": obj})
+            sentry_sdk.capture_exception(e)
             return None
 
     def serialize(