[mod] Upgrade Sphinx from 6.2.1 to 7.0.1
To upgrade Sphinx, MyST-Parser and markdown-it-py must also be updated at the
same time:
Closes: https://github.com/searxng/searxng/pull/2433
Closes: https://github.com/searxng/searxng/pull/2492
Closes: https://github.com/searxng/searxng/pull/2504
Signed-off-by: Markus Heiser <markus.heiser@darmarit.de>