AUC sorting inconsistency

[JanBenisek]

We found a small inconsistency - in plot_univariate_predictor_quality() we sort by 'AUC train'

cobra/cobra/evaluation/plotting_utils.py

Lines 26 to 27 in 0133435

	df = (df_auc[df_auc["preselection"]]
	.sort_values(by='AUC train', ascending=False))

while in compute_univariate_preselection() we sort by 'AUC selection'.

cobra/cobra/model_building/univariate_selection.py

Lines 91 to 92 in 0133435

	return (df_auc.sort_values(by='AUC selection', ascending=False)
	.reset_index(drop=True))

It does not ahve any effect on the modeling, but then the plot and preselected_predictors have different order of variables, which is confusing.

Both should be sorted by 'AUC selection'.