capstone: Allow version 3.0.5 again

According to

 https://lore.kernel.org/qemu-devel/20200921174118.39352-1-richard.henderson@linaro.org/



there was an issue with Capstone 3.0.4 from Ubuntu 18, which was the reason
for bumping our minimum Capstone requirement to version 4.0. And indeed,
compiling with that version 3.0.4 from Ubuntu 18.04 still fails (after
allowing it with a hack in meson.build). But now that we've dropped support
for Ubuntu 18.04, that issue is not relevant anymore. Compiling with Capstone
version 3.0.5 (e.g. used in Ubuntu 20.04) seems to work fine, so let's allow
that version again.

Message-Id: <20220516145823.148450-3-thuth@redhat.com>
Reviewed-by: Richard Henderson <richard.henderson@linaro.org>
Signed-off-by: Thomas Huth <thuth@redhat.com>