bump libslirp to v4.9.0

[AkihiroSuda]

https://gitlab.freedesktop.org/slirp/libslirp/-/blob/v4.9.0/CHANGELOG.md

[AkihiroSuda]

https://github.com/rootless-containers/slirp4netns/actions/runs/13223274029/job/36910924365?pr=351

make lint
make[1]: Entering directory '/slirp4netns'
clang-tidy -warnings-as-errors='*' --checks='-clang-analyzer-security.insecureAPI.DeprecatedOrUnsafeBufferHandling' main.c slirp4netns.c api.c sandbox.c seccompfilter.c -- -I/usr/include/glib-2.0 -I/usr/lib/x86_64-linux-gnu/glib-2.0/include -I/usr/local/include/slirp -I/usr/include/glib-2.0 -I/usr/lib/x86_64-linux-gnu/glib-2.0/include  
3 warnings generated.
3 warnings generated.
3 warnings generated.
3 warnings generated.
/slirp4netns/slirp4netns.c:246:6: error: 'register_poll_fd' is deprecated [clang-diagnostic-deprecated-declarations,-warnings-as-errors]
3 warnings treated as errors
    .register_poll_fd = libslirp_register_poll_fd,
     ^
/usr/local/include/slirp/libslirp.h:134:52: note: 'register_poll_fd' has been explicitly marked deprecated here
    void (*register_poll_fd)(int fd, void *opaque) SLIRP_DEPRECATED;
                                                   ^
/usr/local/include/slirp/libslirp.h:40:41: note: expanded from macro 'SLIRP_DEPRECATED'
#define SLIRP_DEPRECATED __attribute__((__deprecated__))
                                        ^
/slirp4netns/slirp4netns.c:247:6: error: 'unregister_poll_fd' is deprecated [clang-diagnostic-deprecated-declarations,-warnings-as-errors]
    .unregister_poll_fd = libslirp_unregister_poll_fd,
     ^
/usr/local/include/slirp/libslirp.h:136:54: note: 'unregister_poll_fd' has been explicitly marked deprecated here
    void (*unregister_poll_fd)(int fd, void *opaque) SLIRP_DEPRECATED;
                                                     ^
/usr/local/include/slirp/libslirp.h:40:41: note: expanded from macro 'SLIRP_DEPRECATED'
#define SLIRP_DEPRECATED __attribute__((__deprecated__))
                                        ^
/slirp4netns/slirp4netns.c:375:9: error: 'slirp_pollfds_fill' is deprecated [clang-diagnostic-deprecated-declarations,-warnings-as-errors]
        slirp_pollfds_fill(slirp, &timeout, libslirp_add_poll, pollfds);
        ^
/usr/local/include/slirp/libslirp.h:274:64: note: 'slirp_pollfds_fill' has been explicitly marked deprecated here
                        SlirpAddPollCb add_poll, void *opaque) SLIRP_DEPRECATED;
                                                               ^
/usr/local/include/slirp/libslirp.h:40:41: note: expanded from macro 'SLIRP_DEPRECATED'
#define SLIRP_DEPRECATED __attribute__((__deprecated__))
                                        ^
make[1]: *** [Makefile:1500: lint] Error 1