fix bad link to launch game template

game_template.html

@@ -39,7 +39,7 @@
       <p>By Flutter</p>
       <div class="toolbar">
         <div class="buttons">
-          <button class="mdc-button mdc-button--outlined" onclick="window.location.href = 'web/material_3_demo';"><span class="mdc-button__ripple"></span> Launch App</button><button class="mdc-button mdc-button--outlined" onclick="window.location.href = 'https://github.com/flutter/samples/tree/master/game_template';">
+          <button class="mdc-button mdc-button--outlined" onclick="window.location.href = 'web/game_template';"><span class="mdc-button__ripple"></span> Launch App</button><button class="mdc-button mdc-button--outlined" onclick="window.location.href = 'https://github.com/flutter/samples/tree/master/game_template';">
       <div class="mdc-button__ripple"></div>
       <i class="material-icons mdc-button__icon" aria-hidden="true">code</i>
       <span class="mdc-button__label">Source Code</span>