Incorrect API usage in system.admin.inc

Also referencing Issues:
#820816: #type text_format not compatible with system_settings_form($automatic_defaults = TRUE)
and
#266246: Add smart defaults for system_settings_form

on line 1584 of systems.admin.inc, system_settings_form is being passed a second parameter when the api does not show support for it. After looking into the patches in the above listed issues I see this was fixed in other functions but looks like it was missed on system_cron_settings.