Rename JSX files with proper .jsx extension (#23733)

app/javascript/mastodon/components/load_pending.js

@@ -1,22 +0,0 @@
-import React from 'react';
-import { FormattedMessage } from 'react-intl';
-import PropTypes from 'prop-types';
-
-export default class LoadPending extends React.PureComponent {
-
-  static propTypes = {
-    onClick: PropTypes.func,
-    count: PropTypes.number,
-  };
-
-  render() {
-    const { count } = this.props;
-
-    return (
-      <button className='load-more load-gap' onClick={this.props.onClick}>
-        <FormattedMessage id='load_pending' defaultMessage='{count, plural, one {# new item} other {# new items}}' values={{ count }} />
-      </button>
-    );
-  }
-
-}