Merge pull request #10429 from wxzs5:fix-documentation

doc/py_tutorials/py_feature2d/py_surf_intro/py_surf_intro.markdown

@@ -147,7 +147,7 @@ Finally we check the descriptor size and change it to 128 if it is only 64-dim.
  False
 
 # So we make it to True to get 128-dim descriptors.
->>> surf.extended = True
+>>> surf.setExtended(True)
 >>> kp, des = surf.detectAndCompute(img,None)
 >>> print( surf.descriptorSize() )
 128

doc/py_tutorials/py_video/py_bg_subtraction/py_bg_subtraction.markdown

@@ -48,7 +48,7 @@ import cv2 as cv
 
 cap = cv.VideoCapture('vtest.avi')
 
-fgbg = cv.createBackgroundSubtractorMOG()
+fgbg = cv.bgsegm.createBackgroundSubtractorMOG()
 
 while(1):
     ret, frame = cap.read()
@@ -125,7 +125,7 @@ import cv2 as cv
 cap = cv.VideoCapture('vtest.avi')
 
 kernel = cv.getStructuringElement(cv.MORPH_ELLIPSE,(3,3))
-fgbg = cv.createBackgroundSubtractorGMG()
+fgbg = cv.bgsegm.createBackgroundSubtractorGMG()
 
 while(1):
     ret, frame = cap.read()