BHV-10987 Minor adjustment on ContextualPopup.less to simplify its CSS o...

...utput Enyo-DCO-1.1-Signed-off-by: Brooke Peterson <brooke.peterson@lge.com>

This is something I should've thought about with BHV-10659BHV, the mixin class ".moon-popup-nub-position" margin should've used shorthand which will reduce quiet a few lines of CSS output.