Customizer @link-color-hover fix

Created by: NinoD

Customize >> Colors >> @link-color-hover is not working properly.

Either it's not working properly when compiling .css or #10172 (closed) #issuecomment-23293444

it's been dropped in v.3 ( hover is only generated as darken(@link-color, 15%) ). Then @link-color-hover should be removed from customizer form.