docs: remove test helper setup (#1842)

docs/app/templates/public-pages/docs/migrate-7-0-to-8-0.hbs

@@ -21,6 +21,9 @@
     See our <a href="https://github.com/cibernox/ember-power-select/blob/8ffe2bc74373f7b1ec8e244bff218c39ba70c19e/ember-power-select/src/components/power-select/options.hbs#L23" target="_blank" rel="noopener noreferrer">options.hbs</a>
     </p>
   </li>
+  <li>
+    <p>Test helpers: The <code>registerPowerSelectHelpers</code> is not required anymore. Please, remove this from <code>/tests/helpers/start-app.js</code>.</p>
+  </li>
   <li>
     <p>Helper: The helper <code>ember-power-select-is-selected</code> was renamed to <code>ember-power-select-is-equal</code>. If you have used in your custom components, you need to replace it</p>
   </li>

docs/app/templates/public-pages/docs/test-helpers.hbs

@@ -8,23 +8,6 @@
   that make it nicer to interact with the component in acceptance tests.
 </p>
 
-<p>
-  To use those helpers in acceptance tests that use <code>moduleForAcceptance</code>, you need to register them in the <code>/tests/helpers/start-app.js</code>
-  file.
-</p>
-
-<p>
-  For that import the registration function and invoke it immedialty.
-</p>
-
-<CodeSnippet @name="test-helpers-1-js.js"/>
-
-<p>
-  However if you are using the new testing API described in
-  <a href="https://github.com/emberjs/rfcs/pull/232">RFC 232</a>, available in ember-cli-qunit >= 4.2 and ember-cli-mocha >= 0.15.0, then you just can explicitly import those
-  helpers where needed (even in integration tests!)
-</p>
-
 <CodeSnippet @name="test-helpers-10-js.js"/>
 
 <h2 class="t3"><code>selectChoose(cssPath, optionTextOrOptionSelector, index?)</code></h2>