[services] Blob - Fix Dockerfile

Summary:
D4493 ruined building blob service using yarn scripts.

@jon Please, take a look here and let me know if this is a nix-friendly change.

Test Plan:

cd services
yar run-backup-service-in-sandbox

Reviewers: jon, marcin, tomek

Reviewed By: jon, marcin

Subscribers: jon, ashoat, tomek, atul, abosh

Differential Revision: https://phab.comm.dev/D4895