Remove Docker Dead book (#3322)

free-programming-books.md

@@ -564,7 +564,6 @@
 * [SVG Essentials](http://commons.oreilly.com/wiki/index.php/SVG_Essentials)
 * [The Quest for Artificial Intelligence: A History of Ideas and Achievements](http://ai.stanford.edu/~nilsson/QAI/qai.pdf) - Nils J. Nilsson (PDF)
 * [Trends Shaping the London Tech Scene](http://www.oreilly.com/programming/free/trends-shaping-the-london-tech-scene.csp) (email address *requested*, not required)
-* [What You Need to Know about Docker](https://www.packtpub.com/packt/free-ebook/what-you-need-know-about-docker) - Scott Gallagher, Packt. (email address *requested*, not required)
 
 
 #### MOOC