Update part-four.html

Remove an unnecessary underscore in part-four.html

Author: ccesare

_includes/sxs/part-four.html

@@ -30,7 +30,7 @@ <h4 class="filename"><span class="material-icons" aria-hidden="true">description
   <h3 class="step">Add USWDS JavaScript to the end of the page body.</h3>
   <p class="step-description">Finally, add the USWDS JavaScript to the end of the page <strong>body</strong>.</p>
   <div class="editor">
-    <h4 class="filename"><span class="material-icons" aria-hidden="true">description</span> ./_layouts_/default.html</h4>
+    <h4 class="filename"><span class="material-icons" aria-hidden="true">description</span> ./_layouts/default.html</h4>
     <pre class="blur">...
 
 &lt;body class="&lcub;&lcub; page.body &rcub;&rcub;"&gt;
@@ -41,4 +41,4 @@ <h4 class="filename"><span class="material-icons" aria-hidden="true">description
   </div>
   <p class="step-description"><strong>Note:</strong> You've added USWDS styles and JavaScript to your project, but you shouldn't see any changes to the existing site. It still looks the same! We've designed USWDS for incremental adoption on existing sites. In most cases, you won't see the effects of USWDS code until you intentionally add USWDS components.</p>
   <p class="step-description">At this point, you've added USWDS design system code to your project successfully! Now we can add some components.</p>
-</section>
+</section>