doc: Upgrade docutils.sourceforge.io links to HTTPS

Also change any docutils.sourceforge.net link to io
top level domain.

doc/usage/configuration.rst

@@ -18,8 +18,8 @@ and output behavior.
   directory to adjust `Docutils`_ configuration if not otherwise overridden or
   set by Sphinx.
 
-  .. _`docutils`: http://docutils.sourceforge.net/
-  .. _`docutils.conf`: http://docutils.sourceforge.net/docs/user/config.html
+  .. _`docutils`: https://docutils.sourceforge.io/
+  .. _`docutils.conf`: https://docutils.sourceforge.io/docs/user/config.html
 
 The configuration file is executed as Python code at build time (using
 :func:`execfile`, and with the current directory set to its containing
@@ -484,7 +484,7 @@ General configuration
    languages, will be used to convert quotes and dashes to typographically
    correct entities.  Default: ``True``.
 
-   __ http://docutils.sourceforge.net/docs/user/smartquotes.html
+   __ https://docutils.sourceforge.io/docs/user/smartquotes.html
    __ https://daringfireball.net/projects/smartypants/
 
    .. versionadded:: 1.6.6
@@ -497,8 +497,8 @@ General configuration
    *deactivates* smart quotes via the corresponding `Docutils option`__.  But
    if it *activates* them, then :confval:`smartquotes` does prevail.
 
-   __ http://docutils.sourceforge.net/docs/user/config.html
-   __ http://docutils.sourceforge.net/docs/user/config.html#smart-quotes
+   __ https://docutils.sourceforge.io/docs/user/config.html
+   __ https://docutils.sourceforge.io/docs/user/config.html#smart-quotes
 
 .. confval:: smartquotes_action
 

doc/usage/extensions/napoleon.rst

@@ -49,7 +49,7 @@ parse them. This happens in an intermediate step while Sphinx is processing
 the documentation, so it doesn't modify any of the docstrings in your actual
 source code files.
 
-.. _ReStructuredText: http://docutils.sourceforge.net/rst.html
+.. _ReStructuredText: https://docutils.sourceforge.io/rst.html
 .. _docstrings: https://www.python.org/dev/peps/pep-0287/
 .. _Google Python Style Guide:
    https://google.github.io/styleguide/pyguide.html

doc/usage/restructuredtext/basics.rst

@@ -15,7 +15,7 @@ language, this will not take too long.
 .. seealso::
 
    The authoritative `reStructuredText User Documentation
-   <http://docutils.sourceforge.net/rst.html>`_.  The "ref" links in this
+   <https://docutils.sourceforge.io/rst.html>`_.  The "ref" links in this
    document link to the description of the individual constructs in the reST
    reference.
 

doc/usage/restructuredtext/index.rst

@@ -12,7 +12,7 @@ The below guides go through the most important aspects of reST. For the
 authoritative reStructuredText reference, refer to the `docutils
 documentation`__.
 
-__ http://docutils.sourceforge.net/rst.html
+__ https://docutils.sourceforge.io/rst.html
 
 .. toctree::
    :maxdepth: 2