[native] Don't call dispatch from reducer

Summary: Originally, this diff was just making sure that the dispatch didn't occur before REHYDRATE. But when testing that change I found that calling dispatch from a reducer triggered an error. More context in this comment, but this diff is now just removing the dispatch, with the expectation that the error-handling functionality here will be improved following the work in ENG-1974.

Test Plan:
I tested to make sure the app was still killed if an exception was thrown. I also tested that the dispatch error did not get thrown anymore:

You may not call store.getState() while the reducer is executing. The reducer has already received the state as an argument. Pass it down from the top reducer instead of reading it from the store.

Reviewers: atul, tomek, kamil

Reviewed By: atul, kamil

Subscribers: jacek, marcin, kamil

Differential Revision: https://phab.comm.dev/D5672