Update bug last change time parsing logic (#2712)

Author: suhaibmujahid

bugbot/rules/webcompat_platform_without_keyword.py

@@ -5,6 +5,8 @@
 from datetime import datetime
 from typing import Any, Optional
 
+from dateutil import parser
+
 from bugbot import gcp
 from bugbot.bzcleaner import BzCleaner
 
@@ -39,8 +41,7 @@ def handle_bug(
         # so prefer to do nothing.
         if (
             self.last_bugzilla_import_time
-            and datetime.fromisoformat(bug["last_change_time"])
-            > self.last_bugzilla_import_time
+            and parser.parse(bug["last_change_time"]) > self.last_bugzilla_import_time
         ):
             return None