fix(htmlimage): reduced amount of imageObserver padding

Author: jsimck

src/image/HtmlImage.jsx

@@ -173,10 +173,7 @@ export default class HtmlImage extends React.PureComponent {
     let extendedPadding =
       this.props.extendedPadding ||
       Math.max(
-        Math.round(
-          $UIComponentHelper.componentPositions.getWindowViewportRect().height *
-            2
-        ),
+        Math.round($UIComponentHelper.componentPositions.getWindowViewportRect().height),
         MIN_EXTENDED_PADDING
       );