Change help message to fix issue on 3.14

or the $(ascitime) is trying to get interpolated which fails.

Author: Carreau

traitlets/config/application.py

@@ -215,7 +215,8 @@ def _classes_inc_parents(
     _log_formatter_cls = LevelFormatter
 
     log_datefmt = Unicode(
-        "%Y-%m-%d %H:%M:%S", help="The date format used by logging formatters for %(asctime)s"
+        "%Y-%m-%d %H:%M:%S",
+        help="The date format used by logging formatters for `asctime`",
     ).tag(config=True)
 
     log_format = Unicode(