[terraform] upgrade identity staging image to 0.27-staging

Summary:
Upgrades staging to 0.27-staging image, resolving https://linear.app/comm/issue/ENG-8611/identity-user-search-not-working-on-staging

Depends on D12621

Test Plan:
after terraform apply, healthy ecs tasks. Confirmed that identity search was restored by connecting through local iOS simulator

Reviewers: varun

Reviewed By: varun

Subscribers: ashoat, tomek

Differential Revision: https://phab.comm.dev/D12622