Summary:
We detect when a thread is removed from the thread-list by listening to
`Actions.threadListDidUpdate`. However, we were not firing the action at
the correct moment.

Before this commit, we fired the action on the root `ThreadList`'s
`componentDidUpdate`, however did this not actually fire when the
child list actually updated/removed threads from the list.

This sort of used to work because before 396a027bcb6b589fb37cd200b21a01273809ff5c
the root ThreadList component re-rendered all the time, so it fired the
action, but after initial sync, we would never actually report any
thread-list action metrics at all

Test Plan: manual

Reviewers: spang, halla, evan

Reviewed By: halla, evan

Differential Revision: https://phab.nylas.com/D4051