fixed doc warning

modules/ml/doc/ertrees.rst

@@ -9,7 +9,7 @@ Extremely randomized trees have been introduced by Pierre Geurts, Damien Ernst a
 
 
 CvERTrees
---------
+----------
 .. ocv:class:: CvERTrees
 
     The class implements the Extremely randomized trees algorithm. ``CvERTrees`` is inherited from :ocv:class:`CvRTrees` and has the same interface, so see description of :ocv:class:`CvRTrees` class to get detailes. To set the training parameters of Extremely randomized trees the same class :ocv:class:`CvRTParams` is used.