Ok, I found the declaration of the add_menu_page function and found that this is how you can change your code:
Was:
add_menu_page('Section', 'Section', 10, __FILE__, 'section');
add_submenu_page(__FILE__, 'Edit', 'Edit', 10, 'section-edit', 'section_edit');
Fixed:
add_menu_page('Section', 'Section', 10, __FILE__, 'section');
add_submenu_page(__FILE__, 'Edit', 'Edit', 10, __FILE__, 'section_edit');
I personally use basename(__FILE__), so it would look like:
add_menu_page('Section', 'Section', 10, basename(__FILE__), 'section');
add_submenu_page(basename(__FILE__), 'Edit', 'Edit', 10, basename(__FILE__), 'section_edit');
Hope this helps.