Corrected typo in py_histogram_begins tutorial

doc/py_tutorials/py_imgproc/py_histograms/py_histogram_begins/py_histogram_begins.markdown

@@ -46,7 +46,7 @@ histograms](http://docs.opencv.org/doc/tutorials/imgproc/histograms/histogram_ca
 
 So what you do is simply split the whole histogram to 16 sub-parts and value of each sub-part is the
 sum of all pixel count in it. This each sub-part is called "BIN". In first case, number of bins
-where 256 (one for each pixel) while in second case, it is only 16. BINS is represented by the term
+were 256 (one for each pixel) while in second case, it is only 16. BINS is represented by the term
 **histSize** in OpenCV docs.
 
 **DIMS** : It is the number of parameters for which we collect the data. In this case, we collect