Update xml/System.Runtime.InteropServices/ICustomMarshaler.xml

Co-authored-by: Genevieve Warren <24882762+gewarren@users.noreply.github.com>

Author: AaronRobinsonMSFT

xml/System.Runtime.InteropServices/ICustomMarshaler.xml

@@ -124,7 +124,7 @@ const IID IID_IOld = {0x9B2BAADD,0x0705,0x11D3,{0xA0,0xCD,0x00,0xC0,0x4F,0xA3,0x
  Returns the size of the unmanaged data to be marshaled. 
  
 ## Implementing the GetInstance Method 
- In addition to implementing the <xref:System.Runtime.InteropServices.ICustomMarshaler> interface, custom marshalers must implement a `static` method called `GetInstance` that accepts a <xref:System.String> as a parameter and has a return type of <xref:System.Runtime.InteropServices.ICustomMarshaler>. This `static` method is called by the common language runtime's COM interop layer to instantiate an instance of the custom marshaler. The string that is passed to `GetInstance` is a cookie that the method can use to customize the returned custom marshaler. A minimal, but complete, <xref:System.Runtime.InteropServices.ICustomMarshaler> implementation in the form of the `NewOldMarshaler` type is below. 
+ In addition to implementing the <xref:System.Runtime.InteropServices.ICustomMarshaler> interface, custom marshalers must implement a `static` method called `GetInstance` that accepts a <xref:System.String> as a parameter and has a return type of <xref:System.Runtime.InteropServices.ICustomMarshaler>. This `static` method is called by the common language runtime's COM interop layer to instantiate an instance of the custom marshaler. The string that is passed to `GetInstance` is a cookie that the method can use to customize the returned custom marshaler. The following example shows a minimal, but complete, <xref:System.Runtime.InteropServices.ICustomMarshaler> implementation. 
  
  [!code-csharp[System.Runtime.InteropServices.ICustomMarshaler#6](~/samples/snippets/csharp/VS_Snippets_CLR_System/system.runtime.interopservices.icustommarshaler/cs/source.cs#6)]