Remove old container sizing comment

Co-authored-by: James Salter <jamess@element.io>

src/components/views/messages/MImageBody.tsx

@@ -361,7 +361,6 @@ export default class MImageBody extends React.Component<IBodyProps, IState> {
 
         const thumbnail = (
             <div className="mx_MImageBody_thumbnail_container" style={{ maxHeight: maxHeight + "px", maxWidth: maxWidth + "px" }} >
-                { /* Calculate aspect ratio, using %padding will size _container correctly */ }
                 { showPlaceholder &&
                     <div className="mx_MImageBody_thumbnail" style={{
                         // Constrain width here so that spinner appears central to the loaded thumbnail