Update link in Machine Learning section (#3406)

* Remove dead link from free-programming-books-tr.md

* Change Django heading to same size as other headings

* Update link for Learning Deep Architectures

* revert django heading

* undo space add

free-programming-books.md

@@ -433,7 +433,7 @@
 * [Information Theory, Inference, and Learning Algorithms](http://www.inference.phy.cam.ac.uk/itila/)
 * [Introduction to Machine Learning](http://arxiv.org/abs/0904.3664v1) - Amnon Shashua
 * [Learn Tensorflow](https://bitbucket.org/hrojas/learn-tensorflow) - Jupyter Notebooks
-* [Learning Deep Architectures for AI](http://www.iro.umontreal.ca/~bengioy/papers/ftml_book.pdf) (PDF)
+* [Learning Deep Architectures for AI](https://mila.quebec/wp-content/uploads/2019/08/TR1312.pdf) (PDF)
 * [Machine Learning](http://www.intechopen.com/books/machine_learning)
 * [Machine Learning, Neural and Statistical Classification](http://www1.maths.leeds.ac.uk/~charles/statlog/)
 * [Neural Networks and Deep Learning](http://neuralnetworksanddeeplearning.com)