fix: remove classses_ attribute from kNN regression (#1224)

Author: ahuber21

sklearnex/neighbors/knn_regression.py

@@ -405,7 +405,6 @@ def _onedal_kneighbors(self, X=None, n_neighbors=None,
             X, n_neighbors, return_distance, queue=queue)
 
     def _save_attributes(self):
-        self.classes_ = self._onedal_estimator.classes_
         self.n_features_in_ = self._onedal_estimator.n_features_in_
         self.n_samples_fit_ = self._onedal_estimator.n_samples_fit_
         self._fit_X = self._onedal_estimator._fit_X