Replaced broken Automata Theory English Stanford course link (#3580)

free-courses-en.md

@@ -436,7 +436,7 @@
 
 ### Theory
 
-* [Automata Theory](https://lagunita.stanford.edu/courses/course-v1:ComputerScience+Automata+Fall2016/about)
+* [Automata Theory](https://online.stanford.edu/courses/soe-ycsautomata-automata-theory)
 * [Intro to Theoretical Computer Science](https://www.udacity.com/course/intro-to-theoretical-computer-science--cs313) (Udacity)