Fixed minor doc issue

doc/py_tutorials/py_imgproc/py_histograms/py_histogram_equalization/py_histogram_equalization.markdown

@@ -35,7 +35,7 @@ img = cv2.imread('wiki.jpg',0)
 hist,bins = np.histogram(img.flatten(),256,[0,256])
 
 cdf = hist.cumsum()
-cdf_normalized = cdf * hist.max()/ cdf.max()
+cdf_normalized = cdf * float(hist.max()) / cdf.max()
 
 plt.plot(cdf_normalized, color = 'b')
 plt.hist(img.flatten(),256,[0,256], color = 'r')