[web] Temporarily remove refs in ThreadSettingsModal altogether

Summary:
The only reason we have the refs is to ref.focus() inputs. That functionality is currently removed and has been replaced by TODO comments.

This diff temporarily removes refs from ThreadSettingsModal and the child "Tab" components. They'll be added back in this stack shortly (eg they'll be brought back to ThreadSettingsModalGeneralTab after state/functionality has been "pushed" down)

Depends on D3764

Test Plan: flow, no changes in functionality since the .focus() lines have already been removed

Reviewers: def-au1t, palys-swm

Reviewed By: palys-swm

Subscribers: ashoat, Adrian, karol-bisztyga, yayabosh

Differential Revision: https://phabricator.ashoat.com/D3821