Support html in thank you page.

Author: robgietema

frontend/packages/volto-form-block/src/schemaFormBlock/ViewSchemaForm.jsx

@@ -138,7 +138,7 @@ const FormBlockView = ({ data, id, properties, metadata, path }) => {
     </Grid>,
   );
 
-  let thankyou = data.thankyou?.data || '';
+  let thankyou = data.thankyou || '';
 
   // Add formfields
   thankyou = thankyou.replace('${formfields}', formfields);

frontend/packages/volto-form-block/src/schemaFormBlock/schema.js

@@ -299,10 +299,8 @@ export const schemaFormBlockSchema = ({ intl, ...props }) => {
         type: 'string',
         title: intl.formatMessage(messages.thankyou),
         description: intl.formatMessage(messages.thankyou_description),
-        widget: 'richtext',
-        default: {
-          data: '${formfields}',
-        },
+        widget: 'textarea',
+        default: '${formfields}',
       },
       captcha: {
         title: intl.formatMessage(messages.captcha),