Refactoring. Removed useless import. (#3254)

original: https://github.com/tootsuite/mastodon/pull/2618

app/javascript/mastodon/components/status_list.js

 import React from 'react';
-import Status from './status';
 import ImmutablePropTypes from 'react-immutable-proptypes';
 import { ScrollContainer } from 'react-router-scroll';
 import PropTypes from 'prop-types';