JS Notifications messages are too low

Example of use: (after XWIKI-11378 is closed)

• On the Panel Wizard, with Firefox, hover the "save layout" button.
• Firefox will display, in the bottom, the URL of the button (which is actually a link)
• Click on the button.
• If you don't move the pointer, you will not see the notification message, because the URL hint is on the top.

See screenshot.