Fix boxel-ui test types

Author: backspace

packages/boxel-ui/test-app/tests/helpers/index.ts

@@ -1,4 +1,3 @@
-import Resolver from 'ember-resolver';
 import {
   // prettier-ignore
   setupApplicationTest as upstreamSetupApplicationTest,
@@ -7,6 +6,7 @@ import {
   // prettier-ignore
   setupTest as upstreamSetupTest,
   // prettier-ignore
+  SetupTestOptions,
 } from 'ember-qunit';
 
 // This file exists to provide wrappers around ember-qunit's