(docs) Nit: fix heading structure (#1012)

Author: devalog

fern/products/docs/pages/component-library/default-components/code-blocks.mdx

@@ -520,7 +520,7 @@ You can override the synchronization of code blocks by setting the `for` prop.
   </Tab>
 </Tabs>
 
-### Embed local code files
+## Embed local code files
 
 <Tabs>
   <Tab title="Example">