Fix some more Javascript linting issues and discrepancies with upstream (#2209)

* Fix typo in flavours/glitch/features/video/index.js

* Fix various linting issues and discrepancies with upstream

app/javascript/flavours/glitch/features/compose/components/privacy_dropdown.jsx

@@ -1,6 +1,5 @@
 import PropTypes from 'prop-types';
 import React from 'react';
-import ImmutablePropTypes from 'react-immutable-proptypes';
 import { defineMessages, injectIntl } from 'react-intl';
 import Dropdown from './dropdown';