Use the new JSX transform (#25064)

app/javascript/mastodon/features/list_timeline/index.jsx

@@ -1,5 +1,5 @@
 import PropTypes from 'prop-types';
-import React from 'react';
+import { PureComponent } from 'react';
 import { Helmet } from 'react-helmet';
 import ImmutablePropTypes from 'react-immutable-proptypes';
 import { FormattedMessage, defineMessages, injectIntl } from 'react-intl';
@@ -30,7 +30,7 @@ const mapStateToProps = (state, props) => ({
   hasUnread: state.getIn(['timelines', `list:${props.params.id}`, 'unread']) > 0,
 });
 
-class ListTimeline extends React.PureComponent {
+class ListTimeline extends PureComponent {
 
   static contextTypes = {
     router: PropTypes.object,