Since commit dcec003d0 we're only using the menu-text class in the admin
layouts. So instead of defining styles for menu-text and then
overwriting them in the admin section, we can define them just in the
admin section.
Since we don't have <img> tags in the menu-text element in the admin
section, we can remove their styles. And we can also remove the styles
we were overriding twice (like `line-height`).
41235f9f02