[services] Delete unused COMM_TEST_SERVICES

Summary:
Part of ENG-4098.
We don't use COMM_TEST_SERVICES anymore - it was used to unit test C++ services and build test-only version of docker images.

Test Plan: Git grep COMM_TEST_SERVICES - no results.

Reviewers: jon, varun

Reviewed By: jon, varun

Subscribers: ashoat, tomek

Differential Revision: https://phab.comm.dev/D8361