Update py_thresholding.markdown

Changed "If the pixel value is smaller than the threshold" to "If the pixel value is smaller than or equal to the threshold" to make the line align with the working of the code.

doc/py_tutorials/py_imgproc/py_thresholding/py_thresholding.markdown

@@ -11,7 +11,7 @@ Simple Thresholding
 -------------------
 
 Here, the matter is straight-forward. For every pixel, the same threshold value is applied.
-If the pixel value is smaller than the threshold, it is set to 0, otherwise it is set to a maximum value.
+If the pixel value is smaller than or equal to the threshold, it is set to 0, otherwise it is set to a maximum value.
 The function **cv.threshold** is used to apply the thresholding.
 The first argument is the source image, which **should be a grayscale image**.
 The second argument is the threshold value which is used to classify the pixel values.