Use Class and Property Decorators (#3730)

ref https://tc39.github.io/proposal-decorators/

app/javascript/mastodon/features/compose/components/upload_form.js

@@ -11,7 +11,8 @@ const messages = defineMessages({
   undo: { id: 'upload_form.undo', defaultMessage: 'Undo' },
 });
 
-class UploadForm extends React.PureComponent {
+@injectIntl
+export default class UploadForm extends React.PureComponent {
 
   static propTypes = {
     media: ImmutablePropTypes.list.isRequired,
@@ -48,5 +49,3 @@ class UploadForm extends React.PureComponent {
   }
 
 }
-
-export default injectIntl(UploadForm);