CONTRIBUTING.md: Update "How to contribute" link

Author: leriomaggio

CONTRIBUTING.md

@@ -141,7 +141,7 @@ You can also [reach us by email][email].
 [github]: https://github.com
 [github-flow]: https://guides.github.com/introduction/flow/
 [github-join]: https://github.com/join
-[how-contribute]: https://egghead.io/series/how-to-contribute-to-an-open-source-project-on-github
+[how-contribute]: https://app.egghead.io/playlists/how-to-contribute-to-an-open-source-project-on-github
 [issues]: https://guides.github.com/features/issues/
 [swc-issues]: https://github.com/issues?q=user%3Aswcarpentry
 [swc-lessons]: https://software-carpentry.org/lessons/