Revert fixes for nb diff identification due to possible impact on perf (microsoft#227144)

Revert fixes for 227143 due to possible impact on perf

Author: DonJayamanne

src/vs/workbench/contrib/notebook/browser/diff/notebookDiffViewModel.ts

@@ -441,16 +441,12 @@ function createDiffViewModels(instantiationService: IInstantiationService, confi
 				);
 			}
 			case 'unchanged': {
-				const originalCell = originalModel.cells[diff.originalCellIndex];
-				const modifiedCell = modifiedModel.cells[diff.modifiedCellIndex];
-				const type = originalCell.equal(modifiedCell) ? 'unchanged' : 'modified';
 				return new SideBySideDiffElementViewModel(
 					model.modified.notebook,
 					model.original.notebook,
-					originalCell,
-					modifiedCell,
-					type,
-					eventDispatcher,
+					originalModel.cells[diff.originalCellIndex],
+					modifiedModel.cells[diff.modifiedCellIndex],
+					'unchanged', eventDispatcher,
 					initData,
 					notebookService
 				);