Revert "applets/budgie-menu: Increase style consistency with major themes"

This partially reverts commit 8a4540197d646c19aa556bcfceea1a546c99f628.
It turns out that for whatever unknown reason we end up with partly green
looking unreadable text with some themes. Only the new darker Numix is
capable of using this correctly, so unfortunately we must leave this
prettiness absent for a while.