Delete 404 WPF sample links

[gewarren]

Contributes to #9757.

Also deleted info about APIs being introduced in .NET Framework 3.5 in the last file since all supported versions are newer than that.

(Hide whitespace changes.)

[dotnet-issue-labeler]

I couldn't figure out the best area label to add to this PR. If you have write-permissions please help me learn by adding exactly one area label.

[learn-build-service-prod]

Learn Build status updates of commit 205addc:

✅ Validation status: passed

File	Status	Preview URL	Details
xml/System.Windows.Controls/ContentPresenter.xml	✅Succeeded	View
xml/System.Windows.Controls/ControlTemplate.xml	✅Succeeded	View
xml/System.Windows.Controls/FlowDocumentReaderViewingMode.xml	✅Succeeded	View
xml/System.Windows.Controls/ItemsControl.xml	✅Succeeded	View
xml/System.Windows.Controls/ListView.xml	✅Succeeded	View
xml/System.Windows.Controls/Panel.xml	✅Succeeded	View
xml/System.Windows.Media.Animation/DoubleAnimationUsingPath.xml	✅Succeeded	View
xml/System.Windows.Media.Animation/PathAnimationSource.xml	✅Succeeded	View
xml/System.Windows.Media.Media3D/AmbientLight.xml	✅Succeeded	View
xml/System.Windows.Media.Media3D/ContainerUIElement3D.xml	✅Succeeded	View
xml/System.Windows.Media.Media3D/EmissiveMaterial.xml	✅Succeeded	View
xml/System.Windows.Media.Media3D/Matrix3D.xml	✅Succeeded	View
xml/System.Windows.Media.Media3D/MeshGeometry3D.xml	✅Succeeded	View
xml/System.Windows.Media.Media3D/Model3DCollection.xml	✅Succeeded	View
xml/System.Windows.Media.Media3D/ModelUIElement3D.xml	✅Succeeded	View
xml/System.Windows.Media.Media3D/PerspectiveCamera.xml	✅Succeeded	View
xml/System.Windows.Media.Media3D/Point3DCollection.xml	✅Succeeded	View
xml/System.Windows.Media.Media3D/PointLight.xml	✅Succeeded	View
xml/System.Windows.Media.Media3D/Transform3DGroup.xml	✅Succeeded	View
xml/System.Windows.Media/CompositionTarget.xml	✅Succeeded	View
xml/System.Windows.Media/ImageBrush.xml	✅Succeeded	View
xml/System.Windows.Media/TileMode.xml	✅Succeeded	View
xml/System.Windows.Media/VisualBrush.xml	✅Succeeded	View
xml/System.Windows/EventTrigger.xml	✅Succeeded	View
xml/System.Windows/MultiTrigger.xml	✅Succeeded	View

This comment lists only the first 25 files in the pull request.
For more details, please refer to the build report.

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[gewarren]

@adegeo Could you review this one?