.NET 11 Preview 4 updates for WPF and WinForms

[adegeo]

WPF didn't contain any changes in .NET 11 Preview 4.
WinForms had this bug fix:

**System.Windows.Forms.Clipboard / DataObject** `Clipboard.GetDataObject().GetImage()` once again returns bitmap images
    placed on the clipboard. After the typed/NRBF clipboard pipeline shipped
    in .NET 10, bitmaps were stored in the typed data store, but
    `DataObject.GetImage` only read from the legacy `GetData` store and
    returned `null`. `DataObject.GetImage` now first tries the typed pipeline
    via `TryGetData<Image>(DataFormats.Bitmap, autoConvert: true, ...)` and
    falls back to the legacy path, matching the behavior of
    `Clipboard.GetImage()`

Update the what's new content to move things from preview 3 to preview 4.

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Associated WorkItem - 576872