contributing_guide.md: fix link to DCO

Author: richvdh

docs/development/contributing_guide.md

@@ -422,8 +422,8 @@ same lightweight approach that the Linux Kernel
 [submitting patches process](
 https://www.kernel.org/doc/html/latest/process/submitting-patches.html#sign-your-work-the-developer-s-certificate-of-origin>),
 [Docker](https://github.com/docker/docker/blob/master/CONTRIBUTING.md), and many other
-projects use: the DCO (Developer Certificate of Origin:
-http://developercertificate.org/). This is a simple declaration that you wrote
+projects use: the DCO ([Developer Certificate of Origin](http://developercertificate.org/)).
+This is a simple declaration that you wrote
 the contribution or otherwise have the right to contribute it to Matrix:
 
 ```