message: update icons in collapsible title
diff: import * as React from 'react';
  -import classNames from 'classnames';
  import { RootState } from '../store/reducers';
  import { connect } from 'react-redux';
  import { toggleCollapsedSection } from '../settings/actions';
  import { Dispatch } from 'redux';
  +import { AppIcon, expandIcon, collapseIcon } from '../shell/icons';
  interface ProvidedProps {
  sectionId: string;
  @@ -42,12 +42,7 @@ class CollapsibleTitle extends React.Component<Props> {
  <>
  <div className="title" onClick={toggle}>
  <span className="collapse-handle">
  - <i
  - className={classNames(
  - 'fa collapse',
  - collapsed ? 'fa-plus-square-o' : 'fa-minus-square-o'
  - )}
  - />{' '}
  + <AppIcon className="collapse" icon={collapsed ? expandIcon : collapseIcon} />{' '}
  <span>{title}</span>
  </span>
  </div>
  