Update getusermedia.html

getusermedia.html

@@ -3841,7 +3841,7 @@ <h2>Implementation Suggestions</h2>
             playback globally, <em>and</em> the page is visible to the user
             (e.g. not during a lock screen). User agents may defer such action
             if it determines significant time has passed that may jeopardize a
-            users' awareness of the earlier capture session.</p>
+            user's awareness of the earlier capture session.</p>
           </li>
           <li>
             <p>A web page <a data-cite="!HTML/#gains-focus">gains focus</a> and