i386: indicate that 'pconfig' feature was removed intentionally

i386: indicate that 'pconfig' feature was removed intentionally

pconfig feature was added in 5131dc433df and removed in 712f807e196.
This patch mark this feature as known to QEMU and removed by
intentinally. This follows the convention of 9ccb9784b57 and f1a23522b03
dealing with 'osxsave' and 'ospke'.

Signed-off-by: Denis V. Lunev <den@openvz.org>
CC: Paolo Bonzini <pbonzini@redhat.com>
CC: Richard Henderson <rth@twiddle.net>
CC: Eduardo Habkost <ehabkost@redhat.com>
Message-Id: <20190719111222.14943-1-den@openvz.org>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>