Fix image cropping and submission for photo ID verify.

Using the available video resolution increasing the image and request
size and server started failing requests. Fixed it by using canvas
width and height.

PROD-499

lms/static/js/verify_student/views/webcam_photo_view.js

@@ -55,9 +55,7 @@
                      if (this.stream) {
                          video = this.getVideo();
                          canvas = this.getCanvas();
-                         canvas.width = video.videoWidth;
-                         canvas.height = video.videoHeight;
-                         canvas.getContext('2d').drawImage(video, 0, 0);
+                         canvas.getContext('2d').drawImage(video, 0, 0, canvas.width, canvas.height);
                          video.pause();
                          return true;
                      }