doc(testing/components): Custom Attribute remove src/ prefix from .withResources

Fixes aurelia#441

Author: baerrach

current/en-us/9. testing/1. components.md

@@ -179,7 +179,7 @@ describe('MyAttribute', () => {
 
   beforeEach(() => {
     component = StageComponent
-        .withResources('src/my-attribute')
+        .withResources('my-attribute')
         .inView('<div my-attribute.bind="color">Bob</div>')
         .boundTo({ color: 'blue' });
   });