remove unused import

src/vs/workbench/browser/dnd.ts

@@ -22,7 +22,7 @@ import { isCodeEditor } from 'vs/editor/browser/editorBrowser';
 import { IEditorIdentifier, GroupIdentifier } from 'vs/workbench/common/editor';
 import { IEditorService, IResourceEditorInputType } from 'vs/workbench/services/editor/common/editorService';
 import { Disposable, IDisposable, DisposableStore } from 'vs/base/common/lifecycle';
-import { addDisposableListener, EventType, asDomUri, addClass } from 'vs/base/browser/dom';
+import { addDisposableListener, EventType, asDomUri } from 'vs/base/browser/dom';
 import { IEditorGroup } from 'vs/workbench/services/editor/common/editorGroupsService';
 import { IWorkspaceEditingService } from 'vs/workbench/services/workspaces/common/workspaceEditing';
 import { withNullAsUndefined } from 'vs/base/common/types';