how to build a lift chart using scikitplot
The mistake is not to have read the documentation ;)

scikitplot.metrics.plot_lift_curve(y_true, y_probas,...)
Parameters:

y_true (array-like, shape (n_samples)) – Ground truth (correct) target values.
y_probas (array-like, shape (n_samples, n_classes)) – Prediction probabilities for each class returned by a classifier.


The second parameter y_probas should be a double-dimension array of the predicted probabilities for every class, not a single dimension array of the predicted class.
You can also check the example provided in the documentation which contains:
y_probas = lr.predict_proba(X_test)