kdtree article: fix link to article

content/articles/kdtree/kdtree.rst

@@ -7,7 +7,7 @@ arbitrary and should not disturb a *non-rustacean* (who doesn't code in rust) re
 
 The implementation I will use is described in the scientific paper `On building fast kd-Trees
 for Ray Tracing, and on doing that in O(N log N)
-<http://www.irisa.fr/prive/kadi/Sujets_CTR/kadi/Kadi_sujet2_article_KDTree.pdf>`_.
+<https://www.irisa.fr/prive/kadi/Sujets_CTR/kadi/Kadi_sujet2_article_Kdtree.pdf>`_.
 Since this paper describes well the theoretical part, I will focus on the
 implementation. However, if you just want to implement a KD tree without diving
 into the paper formulas, you can keep reading without woring.