fix: remove groupsByEvent=false — causes registerUndo to silently fail

With groupsByEvent=false, NSUndoManager requires explicit beginUndoGrouping()
before registerUndo(). Without it, registerUndo throws an exception that AppKit
catches silently, causing all undo registration to be no-ops. This broke cell
edit commit — changes were recorded in the tracking arrays but never registered
with the undo manager.

The default groupsByEvent=true auto-creates groups per run loop pass, which is
correct for individual cell edits.

Author: datlechin

TablePro/Core/ChangeTracking/DataChangeManager.swift

@@ -101,7 +101,6 @@ final class DataChangeManager {
     private let undoManager: UndoManager = {
         let manager = UndoManager()
         manager.levelsOfUndo = 100
-        manager.groupsByEvent = false
         return manager
     }()