Remove scheduler usage from CanExecuteChanged handling

Eliminated the use of ObserveOn and explicit scheduling on the main thread when raising CanExecuteChanged events. This simplifies event invocation and avoids unnecessary scheduler dependencies.

Author: ChrisPulman

src/ReactiveUI/ReactiveCommand/ReactiveCommand.cs

@@ -847,7 +847,6 @@ protected internal ReactiveCommand(
                                              .Select(x => x.Result);
 
         _canExecuteSubscription = _canExecute
-                                  .ObserveOn(_outputScheduler)
                                   .Subscribe(OnCanExecuteChanged);
     }
 

src/ReactiveUI/ReactiveCommand/ReactiveCommandBase.cs

@@ -140,7 +140,7 @@ public void Dispose()
     protected void OnCanExecuteChanged(bool newValue)
     {
         _canExecuteValue = newValue;
-        RxSchedulers.MainThreadScheduler.Schedule(() => _canExecuteChanged?.Invoke(this, EventArgs.Empty));
+        _canExecuteChanged?.Invoke(this, EventArgs.Empty);
     }
 
     /// <summary>