Make types exact

Summary: Native notifications modules JS types can be exact since we established there are no fields in those objects that are not covered by types.

Test Plan: Run flow in native directory. Using console.log ensure types are covering every fields present in those objects.

Reviewers: tomek, bartek, ashoat

Reviewed By: ashoat

Subscribers: ashoat, atul

Differential Revision: https://phab.comm.dev/D6823