setup: drop the hack to disable linker warning 4197 on Windows
I don't see this when building on Windows with py3.8 or py3.12, so either the
code was fixed, or (more likely) the compiler stopped warning about it some time
after VS 2008. If we do have to put this back, it would probably be better to
put a `#pragma` in a header file somewhere, and avoid `setuptools` technical
debt.
#if no-windows
$ mkdir -p xdgconf/hg
$ echo '[ui]' > xdgconf/hg/hgrc
$ echo 'username = foobar' >> xdgconf/hg/hgrc
$ XDG_CONFIG_HOME="`pwd`/xdgconf" ; export XDG_CONFIG_HOME
$ unset HGRCPATH
$ hg config ui.username 2>/dev/null
foobar
#endif