[neutron] Update of the neutron-lib-commit group in the Gerrit

Hi,

In Gerrit we have neutron-lib-core group and members of that group have permission to approve neutron-lib patches in master branch. Until today members of the neutron-drivers-core group were members of that group but I added also neutron-core group there. So now every neutron-core team member can approve neutron-lib patches as well. I think that in current state of our teams and current state of the neutron- lib project, it's perfectly fine and we can trust all our neutron cores and let them approve neutron-lib patches as well. But if You have anything against that, please let me know so we can discuss it on ML or on IRC :)