Fix the predict quantiles docstring

Signed-off-by: Adam Li <adam2392@gmail.com>

Author: adam2392

sklearn/ensemble/_forest.py

@@ -733,9 +733,9 @@ def predict_quantiles(self, X, quantiles=0.5, method="nearest"):
 
         Returns
         -------
-        y : ndarray of shape (n_samples, n_quantiles) or
-                (n_samples, n_quantiles, n_outputs)
-            The predicted values.
+        y : ndarray of shape (n_samples, n_quantiles, [n_output])
+            The predicted values. The ``n_outputs`` dimension is present only
+            for multi-output regressors.
         """
         if not self.store_leaf_values:
             raise RuntimeError(