Remove findDOMNode as per warning

src/app/components/ModalHelp.jsx

@@ -1,7 +1,6 @@
 /* eslint react/no-danger: 0 */
 import PropTypes from 'prop-types';
 import React from 'react';
-import { findDOMNode } from 'react-dom';
 import TranslatedComponent from './TranslatedComponent';
 
 /**
@@ -21,17 +20,6 @@ export default class ModalHelp extends TranslatedComponent {
     super(props);
   }
 
-  /**
-   * Focus on textarea and select all
-   */
-  componentDidMount() {
-    const e = findDOMNode(this.refs.exportField);
-    if (e) {
-      e.focus();
-      e.select();
-    }
-  }
-
   /**
    * Render the modal
    * @return {React.Component} Modal Content