update help text

Author: ftyers

server/public/html/help.html

@@ -53,7 +53,7 @@ <h4>Editing tokens</h4>
     </tr>
     <tr>
       <td>Merge two tokens into a supertoken</td>
-      <td>Left click on a token, then press <kbd>s</kbd>, then select with an arrow, which neighbor you want to merge with it. </td>
+      <td>Left click on a token, then press <kbd>c</kbd>, then select with an arrow, which neighbor you want to merge with it. </td>
     </tr>
   </table>