Update app.js

Updated the calling option timing to show up

Author: Andrea-Orimoto

Node/examples/demo-skype-calling/app.js

@@ -26,7 +26,7 @@ and even send a caller a chat message.
     * To use the bot you'll need to click the join link in the portal which will
       add it as a contact to your skype account. When you click on the bot in 
       your skype client you should see an option to call your bot. If you're 
-      adding calling to an existing bot can take a few minutes for the calling 
+      adding calling to an existing bot can take up to 24 hours for the calling 
       option to show up.
     * You can run the bot by launching it from VSCode or running "node app.js"
       from a console window.  Then call your bot from a skype client to start