yes, params changed a bit:
check_default_parameters={
"expiration_level": ("fixed", (30 * _DAY, 10 * _DAY)),
},
that’s how the SimpleLevels are created now 
and you should use the proper migration function (see /omd/versions/default/lib/python3.12/site-packages/cmk/rulesets/v1/form_specs/_migrations.py)