Sphinx 9 incompatibility

Running our doctests using Sphinx 9+, the context.clear() calls in hidden doctest sections aren't executed causing the following tests to fail since the assembler still uses arm instead of i386.

https://github.com/Gallopsled/pwntools/blob/f55f440c07453e7a2441bb71d155b77f419b2bd2/docs/source/intro.rst?plain=1#L146-L149

We should investigate the problems before updating our monkey-patches in conf.py for Sphinx 9 support (or consider requesting proper hooks upstream).