Update example_tooltip.py

[malekcellier]

It seems the name of that feature has been changed from Tooltip to Balloon but the example was not updated.

For new widgets only:

Title: Merge branch_name into master to add WidgetName widget

PR Details:

• Widget name:
• Author:

Description

A short description of this particular widget.

Checklist

• Widget in a separate file in the appropriate folder
• Widget functions properly on both Windows and Linux
• Widget code includes docstrings with parameter descriptions
• Included an example file in /examples
• Widget is covered by unitttests in /tests
• Widget includes required assets files
• Reference to widget in AUTHORS.md
• Entry in sphinx documentation