docs: add green highlighting to x-fern-sdk-variables code blocks

Co-Authored-By: [email protected] <[email protected]>

Author: devin-ai-integration[bot]

fern/products/api-def/openapi-pages/extensions/sdk-variables.mdx

@@ -15,7 +15,7 @@ SDK variables are defined at the document level using `x-fern-sdk-variables` and
 
 At the document level, define your variables with their types:
 
-```yaml title="openapi.yml"
+```yaml {6-9} title="openapi.yml"
 openapi: 3.0.0
 info:
   title: Plant API
@@ -107,7 +107,7 @@ List<Plant> plants = client.listPlants();
 
 You can define multiple SDK variables for complex path hierarchies:
 
-```yaml title="openapi.yml"
+```yaml {1-8,18,24} title="openapi.yml"
 x-fern-sdk-variables:
   gardenId:
     type: string