[terraform] Provide Blob service addr to Identity env

Summary:
Provide blob service env var in identity terraform config. Nothing more is needed since they both have already been set up in the ECS Sservice Connect namespace

Depends on D13641

Test Plan: terraform plan

Reviewers: will, varun, kamil

Reviewed By: kamil

Subscribers: ashoat, tomek

Differential Revision: https://phab.comm.dev/D13642