DOC Improve narrative of plot_roc_crossval example (#24710)
DOC Improve narrative of plot_roc_crossval example (#24710)

Co-authored-by: Guillaume Lemaitre <e5e78d384e205244ed69377c80930de68a2732ec@gmail.com>
espg/scikit-learn,vinayak-mehta/scikit-learn,espg/scikit-learn,betatim/scikit-learn,scikit-learn/scikit-learn,scikit-learn/scikit-learn,betatim/scikit-learn,vinayak-mehta/scikit-learn,scikit-learn/scikit-learn,scikit-learn/scikit-learn,espg/scikit-learn,espg/scikit-learn,vinayak-mehta/scikit-learn,betatim/scikit-learn,vinayak-mehta/scikit-learn,betatim/scikit-learn