While reviewing MDL-64819 I've seen some legacy code for displaying the +/- buttons which is not used anymore, since MDL-57769 was integrated.
This legacy code can be removed because is not used anywhere (for instance, the method change_number_sections in the course/format/renderer.php file).
MDL-64819 Activity and Section menus duplicate text in icons and labels
MDL-57769 Remove 'numsections' from topics and weeks, allow teachers to create and delete sections as they are needed
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