python: don't use 'cv2.' in documentation

modules/features2d/include/opencv2/features2d.hpp

@@ -488,9 +488,9 @@ FastFeatureDetector::TYPE_5_8
 
 Detects corners using the FAST algorithm by @cite Rosten06 .
 
-@note In Python API, types are given as cv2.FAST_FEATURE_DETECTOR_TYPE_5_8,
-cv2.FAST_FEATURE_DETECTOR_TYPE_7_12 and cv2.FAST_FEATURE_DETECTOR_TYPE_9_16. For corner
-detection, use cv2.FAST.detect() method.
+@note In Python API, types are given as cv.FAST_FEATURE_DETECTOR_TYPE_5_8,
+cv.FAST_FEATURE_DETECTOR_TYPE_7_12 and cv.FAST_FEATURE_DETECTOR_TYPE_9_16. For corner
+detection, use cv.FAST.detect() method.
  */
 CV_EXPORTS void FAST( InputArray image, CV_OUT std::vector<KeyPoint>& keypoints,
                       int threshold, bool nonmaxSuppression, FastFeatureDetector::DetectorType type );
@@ -1224,9 +1224,9 @@ output image. See possible flags bit values below.
 DrawMatchesFlags. See details above in drawMatches .
 
 @note
-For Python API, flags are modified as cv2.DRAW_MATCHES_FLAGS_DEFAULT,
-cv2.DRAW_MATCHES_FLAGS_DRAW_RICH_KEYPOINTS, cv2.DRAW_MATCHES_FLAGS_DRAW_OVER_OUTIMG,
-cv2.DRAW_MATCHES_FLAGS_NOT_DRAW_SINGLE_POINTS
+For Python API, flags are modified as cv.DRAW_MATCHES_FLAGS_DEFAULT,
+cv.DRAW_MATCHES_FLAGS_DRAW_RICH_KEYPOINTS, cv.DRAW_MATCHES_FLAGS_DRAW_OVER_OUTIMG,
+cv.DRAW_MATCHES_FLAGS_NOT_DRAW_SINGLE_POINTS
  */
 CV_EXPORTS_W void drawKeypoints( InputArray image, const std::vector<KeyPoint>& keypoints, InputOutputArray outImage,
                                const Scalar& color=Scalar::all(-1), DrawMatchesFlags flags=DrawMatchesFlags::DEFAULT );