refactor(courses): Move Elements of AI

Moved to  `Artificial Intelligence` section suggested in EbookFoundation#5569 (comment)

Resolves EbookFoundation#5569
Locks Resolves EbookFoundation#5569

Author: davorpa

Diff for: courses/free-courses-en.md

@@ -147,7 +147,7 @@
 
 ### Artificial Intelligence
 
-<!-- Waiting to add in -->
+* [Elements of AI](https://www.elementsofai.com) - University of Helsinki, Reaktor
 
 
 ### Assembly
@@ -621,7 +621,6 @@
 * [Cloud Computing and Development](https://uaceit.com/courses/cloud-computing-and-development) - Ashwin Kumar Ramaswamy (UAceIt)
 * [Computer Graphics](http://nptel.ac.in/courses/106106090/)
 * [CS50’s Introduction to Artificial Intelligence with Python](https://cs50.harvard.edu/ai/2020/) - Brian Yu and David J. Malan (Harvard OpenCourseWare and EdX)
-* [Elements of AI](https://www.elementsofai.com)
 * [Embedded Software Safety](https://www.youtube.com/playlist?list=PLAQopGWlIcyaqDBW1zSKx7lHfVcOmWSWt) (P. Koopman)
 * [FindLectures.com](https://web.archive.org/web/20161219180842/https://www.findlectures.com/?class1=Technology) - Index of conference talks by language / topic (:card_file_box: *archived*)
 * [Introduction to Information Security](https://www.udacity.com/course/intro-to-information-security--ud459)