Add gnocchi to required projects

The latest release of gnocchi is not installable
due to the protobuf version we use in upper constraints.
This change adds gnocchi as a required project so that
it will be cloned by Zuul and added to LIBS_FROM_GIT

Depends-On: https://review.opendev.org/c/openstack/devstack/+/872902

Change-Id: Ie70fec0a79b8c9ba1354cf32d6740ac710976c5c
1 file changed