RichTextBox.ShowSelectionMargin documentation having conflict with actual behavior

### Type of issue

Other (describe below)

### Description

The current documentation states that if the ShowSelectionMargin property is set to true, setting the ScrollBars property to RichTextBoxScrollBars.Horizontal, RichTextBoxScrollBars.Vertical, or RichTextBoxScrollBars.Both will not cause scroll bars to be displayed.

However, in Visual Studio, even with ShowSelectionMargin set to true, the scroll bars are still displayed when ScrollBars is set to Both, Vertical, or Horizontal. VS2019 and 2022 both having the same behavior.

Suggestion: Maybe the documentation can be updated to reflect the actual behavior observed in Visual Studio.

### Page URL

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

### Content source URL

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

### Document Version Independent Id

f3de60ee-46c3-0078-632c-b35fa44355bc

### Article author

@dotnet-bot