fix: doc: creating new kernel was missing active dims
fix: doc: creating new kernel was missing active dims

SheffieldML/GPy,befelix/GPy,esiivola/GPYgradients,esiivola/GPYgradients,befelix/GPy,esiivola/GPYgradients,befelix/GPy,SheffieldML/GPy,esiivola/GPYgradients,befelix/GPy,SheffieldML/GPy,SheffieldML/GPy