fix(demo): fix accept button colspan

Make accept button to occupy two slots in certain form width

Author: mlopezFC

src/test/java/com/flowingcode/vaadin/addons/extendedlogin/TestLoginLayoutView.java

@@ -60,6 +60,7 @@ private FormLayout createChangePasswordForm() {
         new ResponsiveStep("500px", 2));
     // Stretch the username field over 2 columns
     formLayout.setColspan(username, 2);
+    formLayout.setColspan(accept, 2);
     return formLayout;
   }
 }