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

app/javascript/mastodon/features/notifications/components/clear_column_button.jsx

@@ -0,0 +1,18 @@
+import React from 'react';
+import PropTypes from 'prop-types';
+import { FormattedMessage } from 'react-intl';
+import Icon from 'mastodon/components/icon';
+
+export default class ClearColumnButton extends React.PureComponent {
+
+  static propTypes = {
+    onClick: PropTypes.func.isRequired,
+  };
+
+  render () {
+    return (
+      <button className='text-btn column-header__setting-btn' tabIndex='0' onClick={this.props.onClick}><Icon id='eraser' /> <FormattedMessage id='notifications.clear' defaultMessage='Clear notifications' /></button>
+    );
+  }
+
+}