Sidebar titles can contain other RST elements

[javiereguiluz]

In this page: https://raw.githubusercontent.com/symfony/symfony-docs/4.3/testing.rst

We have this sidebar directive:

.. sidebar:: More about the ``request()`` Method:

    The full signature of the ``request()`` method is::

    [...]

The parser doesn't parse request() inside the sidebar title as a <code> element: