fix: remove add_timestamp from noxfile.options (#856)

logging is setup before all tasks,
so it's not possible to use it as noxfile.option.

we could add it after tasks.merge_noxfile_options,
but in this case the logger wouldn't setup early for
tasks.load_nox_module

nox/_options.py

@@ -407,7 +407,6 @@ def _tag_completer(
         group=options.groups["reporting"],
         action="store_true",
         help="Adds a timestamp to logged output.",
-        noxfile=True,
     ),
     _option_set.Option(
         "default_venv_backend",