chore(app/test): remove unused service submodule (#3928)

`linkerd_app_test::service` contains facilities that are unused.

this commit removes this submodule from the `linkerd-app-test` library.

Signed-off-by: katelyn martin <kate@buoyant.io>

Author: cratelyn

linkerd/app/test/src/lib.rs

@@ -27,7 +27,6 @@ pub mod connect;
 pub mod http_util;
 pub mod profile;
 pub mod resolver;
-pub mod service;
 pub mod track;
 
 pub fn resolver<E>() -> resolver::Dst<E> {