ref: remove deprecated usage of unmountComponentAtNode to support react 19 (#379)

Author: echarles

packages/react/src/components/lumino/Lumino.tsx

@@ -5,7 +5,6 @@
  */
 
 import { useRef, useEffect } from 'react';
-import { unmountComponentAtNode } from 'react-dom';
 import { Widget } from '@lumino/widgets';
 
 type LuminoProps = {
@@ -26,7 +25,6 @@ export const Lumino = (props: LuminoProps) => {
       }
       return () => {
         try {
-          unmountComponentAtNode(children.node);
           if (children.isAttached || children.node.isConnected) {
             children.dispose();
             Widget.detach(children);

packages/react/src/components/lumino/LuminoBox.tsx

@@ -5,7 +5,6 @@
  */
 
 import { useRef, useEffect } from 'react';
-import { unmountComponentAtNode } from 'react-dom';
 import { Widget, BoxPanel } from '@lumino/widgets';
 import { Box } from '@primer/react';
 
@@ -30,7 +29,6 @@ export const LuminoBox = (props: LuminoBoxProps) => {
       }
       return () => {
         try {
-          unmountComponentAtNode(boxPanel.node);
           if (boxPanel.isAttached || boxPanel.node.isConnected) {
             boxPanel.dispose();
             Widget.detach(boxPanel);

packages/react/src/components/lumino/ReactPortalWidget.ts

@@ -54,11 +54,6 @@ export abstract class ReactPortalWidget extends Widget {
    */
   protected onBeforeDetach(msg: Message): void {
     // Unmount the component so it can tear down.
-    // TODO unmountComponentAtNode or not?
-    // console.js:213 Warning: unmountComponentAtNode():
-    // The node you're attempting to unmount was rendered by React and is not a top-level container.
-    // Instead, have the parent component update its state and rerender in order to remove this component.
-    //    ReactDOM.unmountComponentAtNode(this.node);
   }
 
   /**