Removed unused `resolver` test helper

no issue

- hangover from older Ember versions

tests/helpers/resolver.js

@@ -1,11 +0,0 @@
-import Resolver from '../../resolver';
-import config from 'ghost-admin/config/environment';
-
-const resolver = Resolver.create();
-
-resolver.namespace = {
-    modulePrefix: config.modulePrefix,
-    podModulePrefix: config.podModulePrefix
-};
-
-export default resolver;