[web] Restyle Focus / Background buttons
The icons were supposed to be dropped, and "Focus" was supposed to change to "Focused". Additionally some styles were changed.
Test Plan: Run web app, checked that buttons display correctly and work as expected.
Reviewers: michal, kuba, kamil
Reviewed By: kamil
Subscribers: ashoat, tomek, atul
Differential Revision: https://phab.comm.dev/D6734