[blob-service] Remove gRPC service, change default port

Summary:
In D8796 we removed last blob gRPC client. This diff removes gRPC server as well.

First part of ENG-4297.

• Deletes all gRPC related code from Blob service.
• Changes default HTTP port to 50053.

Test Plan: HTTP service still works.

Reviewers: michal, varun, patryk, jon

Reviewed By: michal

Subscribers: ashoat, tomek

Differential Revision: https://phab.comm.dev/D8959