[terraform] add comm_services_use_json_logs env variable for json tracing
Summary: Sets the comm services use json logs environmental variable to "true" to print json logs on staging and production
Test Plan: Deployed identity service image to staging and properly seeing json logs
Reviewers: varun, bartek
Reviewed By: varun
Subscribers: ashoat, tomek
Differential Revision: https://phab.comm.dev/D11824