Fix the undirected_weighted_clustering_coefficient to not normalize the c_coeff at the end

[yacineMahdid]

Right now we do not take the null network into consideration at all for these clustering coefficients

We actually don't need to do this last part: norm_average_c_coeff = nanmean(c_coeff)/nanmean(avg_null_network_c_coeff); as the c_coeff are already normalized by the average null network