Fix typo in video_input_psnr_ssim

doc/tutorials/videoio/video-input-psnr-ssim/video_input_psnr_ssim.markdown

@@ -7,7 +7,7 @@ Goal
 Today it is common to have a digital video recording system at your disposal. Therefore, you will
 eventually come to the situation that you no longer process a batch of images, but video streams.
 These may be of two kinds: real-time image feed (in the case of a webcam) or prerecorded and hard
-disk drive stored files. Luckily OpenCV threats these two in the same manner, with the same C++
+disk drive stored files. Luckily OpenCV treats these two in the same manner, with the same C++
 class. So here's what you'll learn in this tutorial:
 
 -   How to open and read video streams