[Buildkite] Add automatic retries to CommTest workflow

Summary: Try to reduce failures when there are intermittent outages of whatever dependencies.

Test Plan: NA

Reviewers: bartek, ashoat

Reviewed By: ashoat

Subscribers: tomek, wyilio

Differential Revision: https://phab.comm.dev/D9569

.buildkite/commtest.yml

@@ -4,6 +4,8 @@ steps:
       - docker-compose#v4.14.0:
           run: commtest
           command: ['bash', 'run-tests-ci.sh']
+          retry:
+            automatic: true
           config:
             - services/docker-compose.yml
             - services/docker-compose.tests.yml