[web] remove deprecated members modals code

Summary:
With the new AddUsersList component being used as our new expereince for adding users, there were some old components that became unused. This diff cleans up all the deprecated code and removes it

Depends on D11066

Test Plan: flow

Reviewers: atul, inka

Reviewed By: atul

Subscribers: ashoat, tomek

Differential Revision: https://phab.comm.dev/D11067