Add change in docs

Author: mkszepp

docs/app/templates/public-pages/docs/migrate-8-0-to-9-0.gts

@@ -52,6 +52,14 @@ import { LinkTo } from '@ember/routing';
         Note: This option was never documented.
       </p>
     </li>
+    <li>
+      <p>
+        Passing
+        <code>@dir</code>
+        to the content component has been removed. Please pass this parameter as
+        a regular HTML attribute instead.
+      </p>
+    </li>
     <li>
       <p>
         If you are using