So that 'Groups' reads out as either 'Administer groups' for those
screenreaders that respect aria-hidden or 'Groups (Administer groups)'
in admin section when dropdown navigation is off to differentiate it
from the 'Groups' in main section.

When the dropdown is on the submenu list is read out so easily
indicates where one is already.

Change-Id: Ia70d742e8940fa6ec35957c97588a2ad719a62df
Signed-off-by: Robert Lyon <robertl@catalyst.net.nz>