Monitor: Drop QMP info from the qemu-monitor.hx file

Monitor: Drop QMP info from the qemu-monitor.hx file

QMP has its own dispatch table and documentation file
(qmp-commands.hx), we can now drop the following QMP specific info
from qemu-monitor.hx:

    o SQMP/EQMP sections
    o The qmp_capabilities command
    o The query-commands command

However, note that QObject handlers entries are not being removed.
This will only happen when we introduce a proper QMP call interface.

Signed-off-by: Luiz Capitulino <lcapitulino@redhat.com>