Also renames the navbar dropdown related CSS terms, to their equivalent popover related terms to accompany the name change of the theme.
This is according to Vlad's design in figma which differs from the style we have in `tooltip-hotkey-hint`. I used font-weight: 500 instead of 400 as it looked nicer and since Vlad used Source Sans Pro as font-family which we don't have.
Fixes #27202