Add note to avoid using this dialog

https://github.com/dotnet/dotnet-api-docs/blob/2c1f01baf150a26d011ca4ef92aaf4239266a7e9/xml/System.Windows.Forms/FolderBrowserDialog.xml#L48

The [documentation of the native version](https://docs.microsoft.com/en-us/windows/win32/api/shlobj_core/nf-shlobj_core-shbrowseforfoldera) recommends to use IFileDialog instead.

It should also be mentioned that [this dialog has a bug](https://stackoverflow.com/questions/6647761/problem-with-folderbrowserdialog) that still exists in Windows 11: When the user creates a new folder within the dialog and directly clicks the ok button, the folder is actually renamed but the dialog returns the name before the renaming.