Remove books that are no longer free. (#5303)

books/free-programming-books-ru.md

@@ -53,7 +53,6 @@
 * [Python](#python)
   * [Django](#django)
 * [R](#r)
-* [Reverse engineering](#reverse-engineering)
 * [Ruby](#ruby)
   * [RSpec](#rspec)
   * [Ruby on Rails](#ruby-on-rails)
@@ -453,11 +452,6 @@
 * [Рандомизация и бутстреп: статистический анализ в биологии и экологии с использованием R.](http://www.ievbras.ru/ecostat/Kiril/Article/A32/Starb.pdf) (PDF)
 
 
-### Reverse engineering
-
-* [Введение в reverse engineering для начинающих](https://beginners.re/RE4B-RU.pdf) - Денис Юричев (PDF)
-
-
 ### Ruby
 
 * [Руководство пользователя](http://linux.yaroslavl.ru/docs/prog/ruby.html) - matz

books/free-programming-books.md

@@ -1020,7 +1020,6 @@ Kerridge (PDF) (email address *requested*, not required)
 
 ### Assembly Language
 
-* [An introduction to reverse engineering for beginners](https://beginners.re/RE4B-EN.pdf) - Dennis Yurichev (PDF)
 * [ARM Assembly Language Programming](http://www.rigwit.co.uk/ARMBook/ARMBook.pdf) - Peter Knaggs (PDF) (:construction: *in process*)
 * [Assemblers And Loaders (1993)](http://www.davidsalomon.name/assem.advertis/asl.pdf) - David Salomon (PDF)
 * [Assembly Language Succinctly](https://www.syncfusion.com/resources/techportal/details/ebooks/assemblylanguage) (PDF)