Fix broken link to free-programming-books.md in books/free-programming-books-en.md (#5602)

* Fix broken link to free-programming-books.md in books/free-programming-books-en.md

* Update free-programming-books-en.md

Author: tomer

books/free-programming-books-en.md

@@ -5,4 +5,6 @@
 
 ### All
 
-* [English](free-programming-books.md) (The list of books in English is here for historical reasons.)
+* [English, By Programming Language](free-programming-books-langs.md)
+  [English, By Subject](free-programming-books-subjects.md)
+  (The list of books in English is here for historical reasons.)