Merge pull request opencv#17360 from mwtarnowski:fix-documentation-imgproc-blur

* fix documentation for cv::blur

* correct the position of ksize parameter

Author: mwtarnowski

modules/imgproc/include/opencv2/imgproc.hpp

@@ -1507,7 +1507,7 @@ The function smooths an image using the kernel:
 
 \f[\texttt{K} =  \frac{1}{\texttt{ksize.width*ksize.height}} \begin{bmatrix} 1 & 1 & 1 &  \cdots & 1 & 1  \\ 1 & 1 & 1 &  \cdots & 1 & 1  \\ \hdotsfor{6} \\ 1 & 1 & 1 &  \cdots & 1 & 1  \\ \end{bmatrix}\f]
 
-The call `blur(src, dst, ksize, anchor, borderType)` is equivalent to `boxFilter(src, dst, src.type(),
+The call `blur(src, dst, ksize, anchor, borderType)` is equivalent to `boxFilter(src, dst, src.type(), ksize,
 anchor, true, borderType)`.
 
 @param src input image; it can have any number of channels, which are processed independently, but