[books] Move HgInit to books (#5475)

books/free-programming-books.md

@@ -2147,7 +2147,7 @@ Kerridge (PDF) (email address *requested*, not required)
 
 ### Mercurial
 
-* [HGInit - Mercurial Tutorial](https://web.archive.org/web/20180926172759/http://hginit.com/) - Joel Spolsky
+* [Hg Init: a Mercurial Tutorial](https://hginit.github.io) - Joel Spolsky
 * [Mercurial: The Definitive Guide](http://hgbook.red-bean.com)
 * [Mercurial: The Definitive Guide 2nd edition](https://book.mercurial-scm.org)
 

courses/free-courses-en.md

@@ -45,7 +45,6 @@
 * [Machine Learning](#machine-learning)
 * [Markdown](#markdown)
 * [Matlab](#matlab)
-* [Mercurial](#mercurial)
 * [Misc](#misc)
 * [.NET](#net)
 * [OCaml](#ocaml)
@@ -534,11 +533,6 @@
 * [MIT 18.S997 Introduction to MATLAB Programming](http://ocw.mit.edu/courses/mathematics/18-s997-introduction-to-matlab-programming-fall-2011/)
 
 
-### Mercurial
-
-* [Hg Init: a Mercurial Tutorial](https://hginit.github.io) - Joel Spolsky
-
-
 ### Misc
 
 * [Advanced Adobe XD (Web Design)](https://webdesign.tutsplus.com/courses/advanced-adobe-xd-for-everyone) - Adi Purdila