fix: flip back in place the output Y axis

tensorflow/playground#163

Author: bamdadfr

src/playground/playground.ts

@@ -1036,7 +1036,7 @@ function drawDatasetThumbnails () {
     let data = dataGenerator (200, 0);
     data.forEach (function (d) {
       context.fillStyle = colorScale (d.label);
-      context.fillRect (w * (d.x + 6) / 12, h * (d.y + 6) / 12, 4, 4);
+      context.fillRect (w * (d.x + 6) / 12, h * (-d.y + 6) / 12, 4, 4);
     });
     d3.select (canvas.parentNode).style ('display', null);
   }