docs: fix code block highlighting for lines starting with spaces (#7356)

www/apps/book/app/advanced-development/events-and-subscribers/data-payload/page.mdx

@@ -15,8 +15,8 @@ The object that the subscriber function receives as a parameter has a `data` pro
 For example:
 
 export const highlights = [
-  ["8", "", "The event's data payload."],
-  ["9", "{ id: string }", "The type of expected data payloads."]
+  ["7", "", "The event's data payload."],
+  ["8", "{ id: string }", "The type of expected data payloads."]
 ]
 
 ```ts title="src/subscribers/product-created.ts" highlights={highlights}