Missing camel case on a `className`

[ftovaro]

Hello Peter

There is a missing camel case for a className in this line, I can do a PR solving the problem if you want.

Great course so far by the way 😄

https://github.com/pkellner/pluralsight-designing-react-components-course-code/blob/414ede0e5d284fdb696e44ac532d0ff17561be86/03-managing-state-among-components/clip-020-adding-header-and-toolbar-to-speakerslist/src/components/SpeakersToolbar.js#L16