Fix Tempest Plugin Registry page for plugins url

There is extra 'openstack/' is added in each plugin url, for example:
- https://opendev.org/openstack/openstack/barbican-tempest-plugin
- https://opendev.org/openstack/x/trio2o

https://docs.openstack.org/tempest/latest/plugin-registry.html

Change-Id: Idc19bedeb171a91079008e79267304158504d932
1 file changed