Update to modern images

services/web/public/stylesheets/app/editor.less

@@ -140,6 +140,7 @@
 		background-image: url(/img/spellcheck-underline.png);
 		@media (-webkit-min-device-pixel-ratio: 2), (min-resolution: 192dpi) {
 			background-image: url(/img/spellcheck-underline@2x.png);
+			background-size: 5px 4px;
 		}
 		background-repeat: repeat-x;
 		background-position: bottom left;