[web] Change search button clickable area

Summary: https://linear.app/comm/issue/ENG-4317/change-button-click-detection-area-in-chat-top-bar.

Test Plan: Run comm app on web and check if space between buttons is clickable.

Reviewers: bartek, tomek, inka, kamil

Reviewed By: bartek, tomek, inka

Subscribers: ashoat, tomek

Differential Revision: https://phab.comm.dev/D8429