Wrong alignment of menu icons of section items

[Aerendir]

Describe the bug

As you can see, the icon is above the label.

To Reproduce

I simply created a MenuItem::section('The label', 'fa fa-jedi');.

(OPTIONAL) Additional context

The problem is caused mainly by the CSS rule display: flex assigned to class #main-menu .menu .menu-icon: disabling the rule display: flex, the icon is correctly positioned before the label.