fixed typo in doc string

Author: fracpete

python/weka/classifiers.py

@@ -1349,7 +1349,7 @@ def test_model_once(self, classifier, inst, store=False):
         :type classifier: Classifier
         :param inst: the Instance to evaluate on
         :type inst: Instance
-        :param store: whether to store the predictions (some statistics in class_details() like AUC require that that)
+        :param store: whether to store the predictions (some statistics in class_details() like AUC require that)
         :type store: bool
         :return: the classification
         :rtype: float