M-step : Update the diagonal matrix W from beta iterative equation
update_w(df, col_id = "id", var_weights, beta_up, df_id, matrix_id)A dataframe
A character value corresponding to id column name
A character value corresponding to the weights variable
A matrix of estimated beta in a specific cluster k
A list of dataframe filter by id levels
A list of design matrices filter by id levels
omega_inv An up-to-date diagonal matrix W