Update tooltip shadow in the clay-charts package defined by Lexicon

[interaminense]

Hey guys, I created this issue because I would like to contribute to the tooltip shadow update that is defined by Lexicon but isn't being applied to clay-charts.

Currently the tooltip is being displayed this way in Clay

The tooltip should appear the way it is in Lexicon

I would like to contribute by sending a Pull request with this fix to help the infrastructure team. What do you think?