DOC: change link to docutil's "raw" directive

Author: mgeier

doc/prolog-and-epilog.ipynb

@@ -19,7 +19,7 @@
     "This can be done with the configuration values `nbsphinx_prolog` and `nbsphinx_epilog` in the file `conf.py`.\n",
     "\n",
     "The prolog and epilog strings can hold arbitrary [reST](http://sphinx-doc.org/rest.html) markup.\n",
-    "Particularly, the [only](http://www.sphinx-doc.org/markup/misc.html#directive-only) and [raw](http://docutils.sourceforge.net/docs/ref/rst/directives.html#raw-data-pass-through) directives can be used to have different content for HTML and LaTeX output.\n",
+    "Particularly, the [only](http://www.sphinx-doc.org/markup/misc.html#directive-only) and [raw](https://docutils.readthedocs.io/en/sphinx-docs/ref/rst/directives.html#raw-data-pass-through) directives can be used to have different content for HTML and LaTeX output.\n",
     "\n",
     "Those strings are also processed by the [Jinja2](http://jinja.pocoo.org/) templating engine.\n",
     "This means you can run Python-like code within those strings.\n",