remove unused.

src/vs/workbench/contrib/notebook/browser/notebookEditorInput.ts

@@ -6,7 +6,7 @@
 import { EditorInput, IEditorInput, GroupIdentifier, ISaveOptions, IMoveResult } from 'vs/workbench/common/editor';
 import { INotebookService } from 'vs/workbench/contrib/notebook/common/notebookService';
 import { URI } from 'vs/base/common/uri';
-import { isEqual, basename, extname } from 'vs/base/common/resources';
+import { isEqual, basename } from 'vs/base/common/resources';
 import { IInstantiationService } from 'vs/platform/instantiation/common/instantiation';
 import { IFilesConfigurationService, AutoSaveMode } from 'vs/workbench/services/filesConfiguration/common/filesConfigurationService';
 import { NotebookEditorModel } from 'vs/workbench/contrib/notebook/common/notebookEditorModel';