showcase: Remove the tooltip from the ExampleViewer component

[RobbyDeLaet]

I'm submitting a...

[ ] Regression (a behavior that used to work and stopped working in a new release)
[x] Bug report  
[ ] Feature request
[ ] Documentation issue or request
[ ] Support request => Please do not submit support request here, instead see https://github.com/NationalBankBelgium/stark/blob/master/CONTRIBUTING.md#got-a-question-or-problem

Current behavior

When hovering over the example viewer, it displays the translation key from the title as a tool-tip.
Even when the mouse-pointer is over another component inside the example viewer.

Expected behavior

Prevent the tool-tip from showing.

[christophercr]

Closed by #584