monitor: Remove obsolete stubs

monitor: Remove obsolete stubs

hmp_info_roms() was removed in commit dd98234c05 ("qapi:
introduce x-query-roms QMP command"),

hmp_info_numa() in commit 1b8ae799d8 ("qapi: introduce
x-query-numa QMP command"),

hmp_info_ramblock() in commit ca411b7c8a ("qapi: introduce
x-query-ramblock QMP command")

and hmp_info_irq() in commit 91f2fa7045 ("qapi: introduce
x-query-irq QMP command").

Signed-off-by: Philippe Mathieu-Daudé <philmd@linaro.org>
Reviewed-by: Daniel P. Berrangé <berrange@redhat.com>
Reviewed-by: Dr. David Alan Gilbert <dave@treblig.org>
Reviewed-by: Michael Tokarev <mjt@tls.msk.ru>
Signed-off-by: Michael Tokarev <mjt@tls.msk.ru>