[networking-guide] Fix incorrect git URL
[networking-guide] Fix incorrect git URL

backport:mitaka

Change-Id: Ifc42b416c534f734fde829ff2bab66585f628f50
Closes-Bug: #1598269

AlekhyaMallina-Vedams/openstack-manuals,AlekhyaMallina-Vedams/openstack-manuals,openstack/openstack-manuals,AlekhyaMallina-Vedams/openstack-manuals,openstack/openstack-manuals,openstack/openstack-manuals,openstack/openstack-manuals