[TransitionHelper] CancellationTokenSource is disposable and needs handling for clean-up

[michael-hawker]

Issue with an inner disposable reference that needs to be cleaned up by the parent class to avoid the C# compiler warning:

 D:\a\Labs-Windows\Labs-Windows\components\TransitionHelper\src\TransitionHelper.Animation.cs(30,29): error CA1001: Type 'TransitionHelper' owns disposable field(s) '_currentAnimationCancellationTokenSource' but is not disposable [D:\a\Labs-Windows\Labs-Windows\components\TransitionHelper\src\CommunityToolkit.Labs.WinUI.TransitionHelper.csproj]

For now this is ignored. Not sure how we want to handle this as it is a resourced helper...

Originally posted by @michael-hawker in #354 (comment)

[michael-hawker]

FYI @JustinXinLiu @Sergio0694 something that came up during porting. Don't think this is a big concern, but something we should understand and address in the future maybe?