add highlighting

Author: devalog

fern/products/sdks/overview/java/configuration.mdx

@@ -94,7 +94,7 @@ as `java.util.String`.
 If you want to customize how your publishing metadata looks in your
 `build.gradle` file, update the `metadata` field in `generators.yml`.
 
-```yml
+```yml {4-9}
     generators:
       - name: fernapi/fern-java-sdk
         version: 2.7.0