Regenerate lexer/parser with ANTLR 4.9.2 I couldn't find the procedure used to generate the previous files documented anywhere, so I made this up which seems to produce a reasonable `git diff`:
I then edited `sphinx_a4doc/syntax/gen/syntax/ANTLRv4Lexer.py` manually to remove `from .LexerAdaptor import LexerAdaptor` imports, which I couldn't find a way to suppress. (There's probably a better way to do this.)
I chose version 4.9.2 partly because it's the version in Debian testing, but also because 4.10 makes an incompatible changes to the format of ATN serialization data, which seemed more invasive. You may want to do that at some point, but for now I thought it was best to get things working on Python 3.13 in a more minimal way.
