Update Reinforcement Learning: An Introduction (#4001)

free-programming-books.md

@@ -488,7 +488,7 @@
 * [Mathematics for Machine Learning](https://gwthomas.github.io/docs/math4ml.pdf) - Garrett Thomas (PDF)
 * [Neural Networks and Deep Learning](http://neuralnetworksanddeeplearning.com)
 * [Probabilistic Models in the Study of Language](http://idiom.ucsd.edu/~rlevy/pmsl_textbook/text.html) (Draft, with R code)
-* [Reinforcement Learning: An Introduction](http://incompleteideas.net/book/bookdraft2017nov5.pdf) - Richard S. Sutton, Andrew G. Barto (PDF)
+* [Reinforcement Learning: An Introduction](http://incompleteideas.net/book/RLbook2020.pdf) - Richard S. Sutton, Andrew G. Barto (PDF)
 * [Speech and Language Processing (3rd Edition Draft)](https://web.stanford.edu/~jurafsky/slp3/ed3book.pdf) - Daniel Jurafsky, James H. Martin (PDF)
 * [The Elements of Statistical Learning](https://web.stanford.edu/~hastie/ElemStatLearn/) - Trevor Hastie, Robert Tibshirani, and Jerome Friedman
 * [The LION Way: Machine Learning plus Intelligent Optimization](https://intelligent-optimization.org/LIONbook/lionbook_3v0.pdf) - Roberto Battiti, Mauro Brunato (PDF)