docs: added code blocks without headers (#2560)

docs/content/add-plugins/mailchimp.md

@@ -61,7 +61,7 @@ const plugins = [
       newsletter_list_id: process.env.MAILCHIMP_NEWSLETTER_LIST_ID
     }
   }
-};
+];
 ```
 
 ## Test it Out
@@ -72,7 +72,7 @@ This plugin adds a new `POST` endpoint at `/mailchimp/subscribe`. This endpoint
 
 Try sending a `POST` request to `/mailchimp/subscribe` with the following JSON body:
 
-```json
+```json noHeader
 {
   "email": "example@gmail.com"
 }
@@ -90,7 +90,7 @@ If you check your Mailchimp dashboard, you should find the email added to your A
 
 Here’s an example of sending additional data with the subscription:
 
-```json
+```json noHeader
 {
     "email": "example@gmail.com",
     "data": {