[web] [fix] tab color active on active selection

Summary:
Tab should be white, per figma

https://linear.app/comm/issue/ENG-890/tab-selection-color-is-in-de-selected-state-when-selected

https://www.figma.com/file/a1nkbWgbgjRlrOY9LVurTz/Comm-%2F-Desktop-app?node-id=1170%3A79583

Test Plan:
change selected color
before:

Reviewers: atul, def-au1t, palys-swm, varun

Reviewed By: palys-swm

Subscribers: ashoat, palys-swm, Adrian, karol-bisztyga

Differential Revision: https://phabricator.ashoat.com/D3452