Fix spelling typos

backport commit 659ffaddb4

modules/ml/include/opencv2/ml.hpp

@@ -1679,7 +1679,7 @@ public:
 
     /** @brief This function returns the trained parameters arranged across rows.
 
-    For a two class classifcation problem, it returns a row matrix. It returns learnt parameters of
+    For a two class classification problem, it returns a row matrix. It returns learnt parameters of
     the Logistic Regression as a matrix of type CV_32F.
      */
     CV_WRAP virtual Mat get_learnt_thetas() const = 0;