Fix broken Financial Numerical Recipes in C++ link (#6213)

* Fix broken Financial Numerical Recipes in C++ link

* Add pdf label

books/free-programming-books-langs.md

@@ -490,7 +490,7 @@ That section got so big, we decided to split it into its own file, the [BY SUBJE
 * [C++ Tricks](http://www.bordoon.com/cplusplus/book_wrapper.html)
 * [CS106X Programming Abstractions in C++](http://web.stanford.edu/class/cs106x/)
 * [Elements of Programming](http://elementsofprogramming.com) - Alexander Stepanov and Paul McJones - (PDF)
-* [Financial Numerical Recipes in C++](http://finance.bi.no/~bernt/gcc_prog/recipes/) - Bernt Arne Ødegaard
+* [Financial Numerical Recipes in C++](https://tfetimes.com/wp-content/uploads/2015/04/recipes.pdf) - Bernt Arne Ødegaard (PDF)
 * [Game Programming Patterns](http://gameprogrammingpatterns.com)
 * [Google's C++ Style Guide](https://google.github.io/styleguide/cppguide.html)
 * [Hands-On System Programming with C++](https://www.packtpub.com/free-ebook/hands-on-system-programming-with-c/9781789137880) - Dr. Rian Quinn (Packt account *required*)