[network-guide] Fix minor issue
[network-guide] Fix minor issue

Fix minor issue with some code-block statements that prevent
rendering.

Change-Id: I7ad7a3d6209969711b9b27d037ebe0ebdc846bcb

saeki-masaki/openstack-manuals,saeki-masaki/openstack-manuals,openstack/openstack-manuals,kairoaraujo/openstack-manuals,AlekhyaMallina-Vedams/openstack-manuals,AlekhyaMallina-Vedams/openstack-manuals,kairoaraujo/openstack-manuals,openstack/openstack-manuals,openstack/openstack-manuals,openstack/openstack-manuals,AlekhyaMallina-Vedams/openstack-manuals,Akasurde/openstack-manuals,potsmaster/openstack-manuals,potsmaster/openstack-manuals,Akasurde/openstack-manuals