Vector: Hide the superfluous "Variants" menu label again

Follow-up to I09c8031c.

Also removed a piece of temporary hacky CSS from Iabda8155.
The other hacks from it were removed, this one persisted.

Bug: 66364
Change-Id: I4d5ae0858e1685a60c42d8080fec2753f25ea9ad
(cherry picked from commit fc67642d0684e5e043ea0c552775adb2787f0026)