[native] Unsubscribe listener on unmount

Summary: In D7525 I forgot to include code that unsubscribes on unmount - this may cause some issues when a user logs out, then logs in and clicks a link.

Test Plan: Log out, log in, click a link - it should work.

Reviewers: bartek, kamil, inka

Reviewed By: bartek

Subscribers: ashoat, atul

Differential Revision: https://phab.comm.dev/D7743