docs: update doxygen-links

One of these URLs are dead these days, and the other one forwards to the
current one, doxygen.nl. Let's get these links up to date.

Signed-off-by: Erik Faye-Lund <erik.faye-lund@collabora.com>
Reviewed-by: Emil Velikov <emil.velikov@collabora.com>
Reviewed-by: Eric Engestrom <eric.engestrom@intel.com>
diff --git a/docs/codingstyle.html b/docs/codingstyle.html
index aa1e09c..1b29663 100644
--- a/docs/codingstyle.html
+++ b/docs/codingstyle.html
@@ -59,7 +59,7 @@
 <li>
 <p>Use comments wherever you think it would be helpful for other developers.
 Several specific cases and style examples follow.  Note that we roughly
-follow <a href="https://www.stack.nl/~dimitri/doxygen/">Doxygen</a> conventions.
+follow <a href="http://www.doxygen.nl">Doxygen</a> conventions.
 </p>
 Single-line comments:
 <pre>