[CI] Run kotlin_tests_mac on EngFlow

In https://github.com/envoyproxy/envoy-mobile/pull/2018 I disabled remote execution for the kotlin_tests_mac CI job because of test failures that were only occurring when using remote execution but ran fine on GitHub Actions workers directly.

Here's the kind of failure we were seeing when running these tests with remote execution: https://github.com/envoyproxy/envoy-mobile/runs/4941854468?check_suite_focus=true

And the same tests running successfully without remote execution: https://github.com/envoyproxy/envoy-mobile/runs/4942623175?check_suite_focus=true