Update CONTRIBUTING.md (#104)

Fixed a broken link

Author: jhvhs

CONTRIBUTING.md

@@ -12,7 +12,7 @@ We have full documentation on how to get started contributing here:
 - Learn how to [change minibroker and try out your changes on a local cluster](README.md#local-development)
 - [Contributor License Agreement](https://git.k8s.io/community/CLA.md) Kubernetes projects require that you sign a Contributor License Agreement (CLA) before we can accept your pull requests
 - [Kubernetes Contributor Guide](https://git.k8s.io/community/contributors/guide) - Main contributor documentation, or you can just jump directly to the [contributing section](https://git.k8s.io/community/contributors/guide#contributing)
-- [Contributor Cheat Sheet](https://git.k8s.io/community/contributors/guide/contributor-cheatsheet.md) - Common resources for existing developers
+- [Contributor Cheat Sheet](https://git.k8s.io/community/contributors/guide/contributor-cheatsheet/) - Common resources for existing developers
 
 ## Mentorship