chore: update agi.mit.edu by Lex Fridman resource (#7074)

Now the link points to http://agi.mit.edu -> https://deeplearning.mit.edu

Addresses Broken links #6942
Resolves #6003

courses/free-courses-en.md

@@ -180,7 +180,7 @@
 * [CS50’s Introduction to Artificial Intelligence with Python](https://cs50.harvard.edu/ai/2020/) - Brian Yu, David J. Malan (Harvard OpenCourseWare and EdX)
 * [Elements of AI](https://www.elementsofai.com) - University of Helsinki, Reaktor
 * [IBM AI Engineering Professional Certificate](https://www.coursera.org/professional-certificates/ai-engineer) - Romeo Kienzler, Saeed Aghabozorgi, Joseph Santarcangelo, Alex Aklson et al. (Coursera)
-* [MIT 6.S099: Artificial General Intelligence](https://agi.mit.edu)
+* [MIT Deep Learning and Artificial Intelligence Lectures](https://deeplearning.mit.edu) - Lex Fridman, et al.
 * [MIT's Artificial Intelligence](http://ocw.mit.edu/courses/electrical-engineering-and-computer-science/6-034-artificial-intelligence-fall-2010/) - Prof. Patrick Henry Winston (MIT OpenCourseWare)