If cannot add restricted profile, don't suggest it

Previously, on devices that cannot add a restricted profile (e.g. most
phones), the Multiple users menu had an option to "Add user", whereas
for devices that can, the option read "Add user or profile". Now it only
says the latter, due to ag/6412347. We add back the original wording
here.

Fixes: 135294519
Test: manual confirmation on a phone that text says "Add user"
Test: m -j ROBOTEST_FILTER=UserSettingsTest RunSettingsRoboTests
Change-Id: Ia166b6ff9c69c0042e8a781be1146a5622177121