[native] Use useRelationshipPrompt hook in RelationshipPrompt

Summary: Switch to newly introduced hook with native RelationshipPrompt.

Test Plan: The prompt behavior didn't change. Tested on virtual iOS device.

Reviewers: palys-swm, benschac, atul, ashoat

Reviewed By: palys-swm, ashoat

Subscribers: benschac, ashoat, Adrian, atul, karol-bisztyga

Differential Revision: https://phabricator.ashoat.com/D2846