Remove unused import

packages/apputils/src/toolbar.tsx

@@ -1,7 +1,7 @@
 // Copyright (c) Jupyter Development Team.
 // Distributed under the terms of the Modified BSD License.
 
-import { ReactWidget, UseSignal, ReactElementWidget } from './vdom';
+import { UseSignal, ReactElementWidget } from './vdom';
 
 import { IIterator, find, map, some } from '@phosphor/algorithm';