[web] deprecate and clean up unused tabs code
Summary:
Now that all the use cases of the tabs component has been updated to use the new tabs component api, we can deprecate our legacy tabs component. Also in this diff took a moment to update the color variables for the tabs style to use the new color design system naming convention
Depends on D10523
Test Plan: flow + confirmed that the tabs had no visual regression
Reviewers: atul, inka
Reviewed By: atul
Subscribers: ashoat, tomek
Differential Revision: https://phab.comm.dev/D10524