Fix broken link to the Coding Horror blog post (#3201)

CONTRIBUTING.md

@@ -109,7 +109,7 @@ Summary of our git branching model:
 - Use [PEP8](https://www.python.org/dev/peps/pep-0008/);
 - Write tests for your new features (please see "Tests" topic below);
 - Always remember that [commented code is dead
-  code](https://www.codinghorror.com/blog/2008/07/coding-without-comments.html);
+  code](https://blog.codinghorror.com/coding-without-comments/);
 - Name identifiers (variables, classes, functions, module names) with readable
   names (`x` is always wrong);
 - When manipulating strings, we prefer either [f-string