Old, inacurate sample

### Type of issue

Code doesn't work

### Description

The sample is good, I guess, for .NET framework, but it does not work as it is given here for .NET 9 (namely, there are no, it seems, classes named ContextMenu and MenuItem in Windows Forms for .NET 9; also, there is no Index property in the ToolStripMenuItem (but MergeIndex) and finally, "object Sender" should be "object? sender", because of nullability checking).

### Page URL

https://learn.microsoft.com/en-us/dotnet/api/system.windows.forms.notifyicon.icon?view=windowsdesktop-9.0

### Content source URL

https://github.com/dotnet/dotnet-api-docs/blob/main/xml/System.Windows.Forms/NotifyIcon.xml

### Document Version Independent Id

def40a46-8e25-83f2-5f48-a6037c4f174a

### Article author

@dotnet-bot