Adjust documentation for Sphinx 4.0.

Discussed upstream at <https://github.com/ganeti/ganeti/pull/1615>.

diff --git a/doc/index.rst b/doc/index.rst
--- a/doc/index.rst
+++ b/doc/index.rst
@@ -119,7 +119,6 @@ Draft designs
    design-hotplug.rst
    design-internal-shutdown.rst
    design-kvmd.rst
-   design-location.rst
    design-linuxha.rst
    design-location.rst
    design-lu-generated-jobs.rst
diff --git a/lib/build/shell_example_lexer.py b/lib/build/shell_example_lexer.py
--- a/lib/build/shell_example_lexer.py
+++ b/lib/build/shell_example_lexer.py
@@ -79,4 +79,4 @@ class ShellExampleLexer(RegexLexer):
 
 
 def setup(app):
-  app.add_lexer("shell-example", ShellExampleLexer())
+  app.add_lexer("shell-example", ShellExampleLexer)
 value='koszko' selected='selected'>koszko</option>
<option value='koszko-scripts'>koszko-scripts</option>
</select> <input type='submit' value='switch'/></form></td></tr>
<tr><td class='sub'>Wojtek's customized Guix</td><td class='sub right'></td></tr></table>
<table class='tabs'><tr><td>
<a href='/guix/about/'>about</a><a href='/guix/'>summary</a><a href='/guix/refs/?id=475b44c9a9b88e9f1b42fc2f29b60b61fc548a43'>refs</a><a class='active' href='/guix/log/po/doc/guix-cookbook.sk.po'>log</a><a href='/guix/tree/po/doc/guix-cookbook.sk.po?id=475b44c9a9b88e9f1b42fc2f29b60b61fc548a43'>tree</a><a href='/guix/commit/po/doc/guix-cookbook.sk.po?id=475b44c9a9b88e9f1b42fc2f29b60b61fc548a43'>commit</a><a href='/guix/diff/po/doc/guix-cookbook.sk.po?id=475b44c9a9b88e9f1b42fc2f29b60b61fc548a43'>diff</a></td><td class='form'><form class='right' method='get' action='/guix/log/po/doc/guix-cookbook.sk.po'>
<input type='hidden' name='id' value='475b44c9a9b88e9f1b42fc2f29b60b61fc548a43'/><select name='qt'>
<option value='grep'>log msg</option>
<option value='author'>author</option>
<option value='committer'>committer</option>
<option value='range'>range</option>
</select>
<input class='txt' type='search' size='10' name='q' value=''/>
<input type='submit' value='search'/>
</form>
</td></tr></table>
<div class='path'>path: <a href='/guix/log/?id=475b44c9a9b88e9f1b42fc2f29b60b61fc548a43'>root</a>/<a href='/guix/log/po?id=475b44c9a9b88e9f1b42fc2f29b60b61fc548a43'>po</a>/<a href='/guix/log/po/doc?id=475b44c9a9b88e9f1b42fc2f29b60b61fc548a43'>doc</a>/<a href='/guix/log/po/doc/guix-cookbook.sk.po?id=475b44c9a9b88e9f1b42fc2f29b60b61fc548a43'>guix-cookbook.sk.po</a></div><div class='content'><table class='list nowrap'><tr class='nohover'><th class='left'>Age</th><th class='left'>Commit message (<a href='/guix/log/po/doc/guix-cookbook.sk.po?id=475b44c9a9b88e9f1b42fc2f29b60b61fc548a43&amp;showmsg=1'>Expand</a>)</th><th class='left'>Author</th></tr>
<tr><td><span title='2022-01-09 11:35:59 +0100'>2022-01-09</span></td><td><a href='/guix/commit/po/doc/guix-cookbook.sk.po?id=934b0cdfee2078bad42429427e12d6ee2ddb7fec'>nls: Update translations.</a><span class='msg-avail'>...<span class='msg-tooltip'>* po/doc/guix-cookbook.fi.po: New file.
* po/doc/guix-manual.fi.po: New file.
* po/doc/local.mk: Add them.
* doc/local.mk: Add them.
* po/guix/fi.po: New file.
* po/guix/LINGUAS: Add it.
</span></span></td><td>Julien Lepiller</td></tr>
<tr><td><span title='2021-10-17 22:10:25 +0200'>2021-10-17</span></td><td><a href='/guix/commit/po/doc/guix-cookbook.sk.po?id=15c91189cb61c579f4289047c79530cefe75215f'>nls: Update translations.</a></td><td>Julien Lepiller</td></tr>