[doc-contrib-guide] Remove jsoncheck
[doc-contrib-guide] Remove jsoncheck

jsoncheck was used for the old API guides and is not used anymore,
it is removed now from openstack-doc-tools, so remove it here as well.

Change-Id: I5c659e6c9d83eaf93f42488d0cd068861bd8af40

openstack/openstack-manuals,openstack/openstack-manuals,openstack/openstack-manuals,openstack/openstack-manuals