[terraform] Remove is-dev conditionals for DDB tables

Summary:
Resolves ENG-4545.

• The identity-users-opaque2 table was dev-only and unused. Introduced in D7241 and removed in D7534
• The walletAddress-index was never enabled on remote. So wallet login was working on dev only.

Test Plan: Terraform plan for staging and prod.

Reviewers: varun

Reviewed By: varun

Subscribers: ashoat, tomek

Differential Revision: https://phab.comm.dev/D11028