CONTRIBUTING: remove IRC contact.

Author: jaragunde

CONTRIBUTING.md

@@ -18,7 +18,3 @@ important for you.
 * **Contribute code**: check the
 [developer documentation](docs/developer/index.rst), then fork our project and
 send us back your contribution as a pull request.
-
-* **Contact**: you can join the IRC channel
-[#phpreport at FreeNode](http://webchat.freenode.net/?channels=#phpreport), or
-contact directly with the project [maintainer](https://github.com/jaragunde).