fix: disable share feature on component unmount (#1048)

* fix: disable share feature on component unmount

* chore: make sure useEffect run only once

Co-authored-by: Leangseu Kim <lkim@edx.org>

src/courseware/course/share/ShareButton.jsx

@@ -1,3 +1,4 @@
+import React from 'react';
 import { PropTypes } from 'prop-types';
 import { useIntl } from '@edx/frontend-platform/i18n';
 import { TwitterShareButton, TwitterIcon } from 'react-share';
@@ -19,6 +20,10 @@ const ShareTwitterIcon = () => (
 function ShareButton({ url }) {
   const { formatMessage } = useIntl();
 
+  React.useEffect(() => () => {
+    window.expSocialShareEnabled = false;
+  }, []);
+
   const twitterUrl = stringifyUrl({
     url,
     query: {