Add links for aria-expended and aria-haspopup

Add 2 missed links on aria page

Author: merciermk

files/en-us/web/accessibility/aria/roles/button_role/index.html

@@ -271,8 +271,8 @@ <h3 id="ARIA_attributes_used">ARIA attributes used</h3>
 <ul>
  <li><code><a href="https://www.w3.org/TR/wai-aria/roles#button">button</a></code></li>
  <li><code><a href="https://www.w3.org/TR/wai-aria-1.1/#aria-pressed">aria-pressed</a></code></li>
- <li><code>aria-expanded</code></li>
- <li><code>aria-haspopup</code></li>
+ <li><code><a href="https://www.w3.org/TR/wai-aria-1.1/#aria-expanded">aria-expanded</a></code></li>
+ <li><code><a href="https://www.w3.org/TR/wai-aria-1.1/#aria-haspopup">aria-haspopup</a></code></li>
 </ul>
 
 <h3 id="Additional_resources">Additional resources</h3>