Max sections setting was deprecated in MDL-84291.

This issue is about the final removal of the setting, which means:

• Remove the setting form the administration form
• Clear the setting on upgrade
• The final deprecation of core_courseformat\base::get_max_sections
• Remove the adminpresets_admin_settings_num_course_sections reference from admin/presets/classes/manager.php (this was replaced during the deprecation of max sections by admin_settings_default_course_sections)