[client-backup] set backup-service prod URL

Summary:
Add URL to deployed service.

There is one problem with this, see: ENG-4852.

Depends on D9066

Test Plan: N/A

Reviewers: michal, marcin, bartek

Reviewed By: michal

Subscribers: ashoat, tomek

Differential Revision: https://phab.comm.dev/D9075