Update stamp.md (#596)

Removed unused API

Author: YoanKar

libraries/radpdfprocessing/model/annotations/stamp.md

@@ -79,7 +79,6 @@ The **AnnotationContentSource** class, accessed by the **Content** property of t
             FormSource simpleForm = new FormSource();
             CreateContentFormWithText(simpleForm, "Sold");
 
-            AnnotationContentSource content = new AnnotationContentSource();
             annotation.Content.NormalContentSource = simpleForm;
             return fixedDocument;
         }
@@ -117,4 +116,4 @@ The **AnnotationContentSource** class, accessed by the **Content** property of t
 * [AcroForm]({%slug radpdfprocessing-model-interactive-forms-acroform %})
 * [FormField]({%slug radpdfprocessing-model-interactive-forms-form-fields%})
 * [Annotations Overview]({%slug radpdfprocessing-model-annotations-overview%})
-* [FormSource]({%slug radpdfprocessing-model-formsource-overview%})
+* [FormSource]({%slug radpdfprocessing-model-formsource-overview%})