[ci skip] Removed link to reSRC.io - site closed

guides/source/getting_started.md

@@ -37,7 +37,6 @@ curve diving straight into Rails. There are several curated lists of online reso
 for learning Ruby:
 
 * [Official Ruby Programming Language website](https://www.ruby-lang.org/en/documentation/)
-* [reSRC's List of Free Programming Books](http://resrc.io/list/10/list-of-free-programming-books/#ruby)
 
 Be aware that some resources, while still excellent, cover versions of Ruby as old as
 1.6, and commonly 1.8, and will not include some syntax that you will see in day-to-day