Remove sCU from Form (#10029)

Related #9790

Form and Form.Item are not considered as pure components

components/form/Form.tsx

@@ -3,7 +3,6 @@ import PropTypes from 'prop-types';
 import classNames from 'classnames';
 import createDOMForm from 'rc-form/lib/createDOMForm';
 import createFormField from 'rc-form/lib/createFormField';
-import PureRenderMixin from 'rc-util/lib/PureRenderMixin';
 import omit from 'omit.js';
 import warning from '../_util/warning';
 import FormItem from './FormItem';
@@ -163,10 +162,6 @@ export default class Form extends React.Component<FormProps, any> {
     warning(!props.form, 'It is unnecessary to pass `form` to `Form` after antd@1.7.0.');
   }
 
-  shouldComponentUpdate(...args: any[]) {
-    return PureRenderMixin.shouldComponentUpdate.apply(this, args);
-  }
-
   getChildContext() {
     const { layout } = this.props;
     return {

components/form/FormItem.tsx

@@ -3,7 +3,6 @@ import * as ReactDOM from 'react-dom';
 import PropTypes from 'prop-types';
 import classNames from 'classnames';
 import Animate from 'rc-animate';
-import PureRenderMixin from 'rc-util/lib/PureRenderMixin';
 import Row from '../grid/row';
 import Col, { ColProps } from '../grid/col';
 import warning from '../_util/warning';
@@ -66,10 +65,6 @@ export default class FormItem extends React.Component<FormItemProps, any> {
     );
   }
 
-  shouldComponentUpdate(...args: any[]) {
-    return PureRenderMixin.shouldComponentUpdate.apply(this, args);
-  }
-
   getHelpMsg() {
     const props = this.props;
     const onlyControl = this.getOnlyControl();