[native] Update the QR login screen to mention the primary device

Summary:
The result of a discussion from D13906.

Depends on D14052

Test Plan: Opened the QR screen and checked if it looks correctly.

Reviewers: kamil, angelika, bartek, ashoat

Reviewed By: ashoat

Subscribers: ashoat

Differential Revision: https://phab.comm.dev/D13946