docs(Field.Number): fix percent demo/example (#3755)

Seems like the `percent` property was forgotten when making the
demo/example, in the following commit
cb89fa4

packages/dnb-design-system-portal/src/docs/uilib/extensions/forms/base-fields/Number/Examples.tsx

@@ -255,6 +255,7 @@ export const Percentage = () => {
   return (
     <ComponentBox>
       <Field.Number
+        percent
         value={80}
         label="Percentage"
         onChange={(value) => console.log('onChange', value)}