Detect typo :mod:`!cgi``

Oh, I'm surprising that sphinx-lint missing this typo in my PR https://github.com/python/cpython/pull/104775 :

```
* :pep:`594`: Remove the :mod:`!cgi`` and :mod:`!cgitb` modules,
  deprecated in Python 3.11.
```

It should be:

```
* :pep:`594`: Remove the :mod:`!cgi` and :mod:`!cgitb` modules,
  deprecated in Python 3.11.
```