Remove unused variables (#3906)

app/javascript/mastodon/features/notifications/components/notification.js

@@ -2,7 +2,6 @@ import React from 'react';
 import ImmutablePropTypes from 'react-immutable-proptypes';
 import StatusContainer from '../../../containers/status_container';
 import AccountContainer from '../../../containers/account_container';
-import Avatar from '../../../components/avatar';
 import { FormattedMessage } from 'react-intl';
 import Permalink from '../../../components/permalink';
 import emojify from '../../../emoji';