Assign a max height of 800px to images in the image dashboard.

The user could always expand to actual dimensions if need be.

PiperOrigin-RevId: 157838046

tensorflow/tensorboard/components/tf_image_dashboard/tf-image-loader.html

@@ -104,6 +104,7 @@ future for loading older images.
         display: block;
         width: 100%;
         height: auto;
+        max-height: 500px;
       }
     </style>
   </template>