[web] fix members modal scrolling behavior

Summary:
This diff address a bug where the members list was not scrolling with the new refactored tabs I introduced a few weeks ago.

Linear task: https://linear.app/comm/issue/ENG-6470/cant-scroll-members-modal-on-web

Test Plan:
Please see the demo video below + also doubled checked with every place that uses the new refactored tabs that they did not have also have any regressions with the scrolling

Reviewers: atul, inka

Reviewed By: inka

Subscribers: ashoat, tomek

Differential Revision: https://phab.comm.dev/D10732