Fix component path

Author: James Mejia

_includes/sxs/02-extending/part-three.html

@@ -94,7 +94,7 @@ <h4 class="filename"><span class="material-icons" aria-hidden="true">description
 <pre class="blur">@use "uswds-core" as *;
 @forward "../assets/css/styles.scss";
 @forward "../assets/css/_my-card.scss";
-</pre><pre class="add">@forward "../assets/css/_my-testimonial.scss";</pre>
+</pre><pre class="add">@forward "../assets/css/components/_my-testimonial.scss";</pre>
   </div>
   <h3 class="step">Start styling the component.</h3>
   <p class="step-description">