Fix "Le langage Caml" (#6608)

* Fix typo
* Update link
* Add author names
* Add "(PDF)"

books/free-programming-books-fr.md

@@ -106,7 +106,7 @@
 
 ### Caml
 
-* [Le language Caml](http://caml.inria.fr)
+* [Le langage Caml](https://caml.inria.fr/pub/distrib/books/llc.pdf) - Pierre Weis, Xavier Leroy (PDF)
 
 
 ### C / C++