[DevTools] Double subscribe/unsubscribe INotifyPropertyChanged

[workgroupengineering]

Describe the bug

Avalonia/src/Avalonia.Diagnostics/Diagnostics/ViewModels/ControlDetailsViewModel.cs

Lines 426 to 434 in 3e3396d

	if (SelectedEntity is INotifyPropertyChanged inpc1)
	{
	inpc1.PropertyChanged -= ControlPropertyChanged;
	}
	if (SelectedEntity is AvaloniaObject ao1)
	{
	ao1.PropertyChanged -= ControlPropertyChanged;
	}

Avalonia/src/Avalonia.Diagnostics/Diagnostics/ViewModels/ControlDetailsViewModel.cs

Lines 452 to 460 in 3e3396d

	if (o is INotifyPropertyChanged inpc2)
	{
	inpc2.PropertyChanged += ControlPropertyChanged;
	}
	if (o is AvaloniaObject ao2)
	{
	ao2.PropertyChanged += ControlPropertyChanged;
	}

To Reproduce
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4. See error

Expected behavior
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Desktop (please complete the following information):

• OS: All
• Version 3e3396d

Additional context
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