Use the new JSX transform (#25064)

app/javascript/mastodon/features/compose/components/upload_progress.jsx

@@ -1,11 +1,11 @@
-import React from 'react';
+import { PureComponent } from 'react';
 import PropTypes from 'prop-types';
 import Motion from '../../ui/util/optional_motion';
 import spring from 'react-motion/lib/spring';
 import { Icon }  from 'mastodon/components/icon';
 import { FormattedMessage } from 'react-intl';
 
-export default class UploadProgress extends React.PureComponent {
+export default class UploadProgress extends PureComponent {
 
   static propTypes = {
     active: PropTypes.bool,