Fix tests failing because of a change in Python 3.10 argparse

Modified from https://github.com/ashb/sphinx-argparse/commit/a7b186aa60cf256dd91268ca3c18e78ef6644223
Removed the changes to CI matrix since it doesn't exist in the PyPI tarball

diff --git a/sphinxarg/parser.py b/sphinxarg/parser.py
index 9a6f76a..89583c6 100644
--- a/sphinxarg/parser.py
+++ b/sphinxarg/parser.py
@@ -154,7 +154,9 @@ def parse_parser(parser, data=None, **kwargs):
             continue
 
         # Upper case "Positional Arguments" and "Optional Arguments" titles
-        if action_group.title == 'optional arguments':
+        # Since python-3.10 'optional arguments' changed to 'options'
+        # more info: https://github.com/python/cpython/pull/23858
+        if action_group.title == 'optional arguments' or action_group.title == 'options':
             action_group.title = 'Named Arguments'
         if action_group.title == 'positional arguments':
             action_group.title = 'Positional Arguments'