check on example using deprecated feature returning plain object instead of Response

[sarah11918]

📚 Subject area/topic

SSR

📋 Page(s) affected (or suggested, for new content)

https://docs.astro.build/en/guides/server-side-rendering/

📋 General description or bullet points (if proposing new content)

Reported on Discord: https://discord.com/channels/830184174198718474/853350631389265940/1175190161991159879

🖥️ Reproduction in StackBlitz (if reporting incorrect content or code samples)

none