Update dynamic-form-item.md

delete unnecessary props

components/form/demo/dynamic-form-item.md

@@ -98,7 +98,6 @@ class DynamicFieldSet extends React.Component {
           <Icon
             className="dynamic-delete-button"
             type="minus-circle-o"
-            disabled={keys.length === 1}
             onClick={() => this.remove(k)}
           />
         ) : null}