[lib] Remove sourceMessageID parameter from useCurrentThreadInfo hook

Summary: We can use sourceMessageID property of threadInfo instead

Test Plan: Open pending sidebar, send a message and verify that the created thread is associated with correct message. Do that on both native and web.

Reviewers: ashoat

Reviewed By: ashoat

Subscribers: KatPo, Adrian, atul

Differential Revision: https://phabricator.ashoat.com/D1149