[native] make reactions prop for InlineEngagement requried

Summary:
In the very next diff we will introduce sending a reaction by pressing on a pill. To prepare for this we need to make reactions prop required so we can use the sendReaction hook

Depends on D8575

Test Plan: flow and confirmed that the InlineEngagement still looks and works as expected for both composed messages and robotext messages

Reviewers: atul, kamil

Reviewed By: kamil

Subscribers: ashoat, tomek

Differential Revision: https://phab.comm.dev/D8576