python: 'cv2.' -> 'cv.' via 'import cv2 as cv'

doc/tutorials/core/adding_images/adding_images.markdown

@@ -86,7 +86,7 @@ Now we need to generate the `g(x)` image. For this, the function **addWeighted()
 
 @add_toggle_python
 @snippet python/tutorial_code/core/AddingImages/adding_images.py blend_images
-Numpy version of above line (but cv2 function is around 2x faster):
+Numpy version of above line (but cv function is around 2x faster):
 \code{.py}
     dst = np.uint8(alpha*(img1)+beta*(img2))
 \endcode

doc/tutorials/core/mat-mask-operations/mat_mask_operations.markdown

@@ -82,7 +82,7 @@ At first we make sure that the input images data in unsigned 8 bit format.
 
 At first we make sure that the input images data in unsigned 8 bit format.
 @code{.py}
-my_image = cv2.cvtColor(my_image, cv2.CV_8U)
+my_image = cv.cvtColor(my_image, cv.CV_8U)
 @endcode
 
 @end_toggle