Mistake in code style

[Met7]

The events example still has underscores at parameters.
https://github.com/OpenZeppelin/openzeppelin-contracts/blob/master/CODE_STYLE.md

[julianmrodri]

I checked the contracts and it is true that we are not using underscore for Event parameters. I submitted a PR to change this example. @abcoathup @nventuro @frangio Feel free to review. Thanks!