Use Render method on SDK to retrieve prompt templates

[saif-shines]

https://github.com/Portkey-AI/portkey-cookbook/blob/main/ai-gateway/how-to-use-openai-sdk-with-portkey-prompt-templates.md

The above cookbook uses axios to retrieve prompt template. Either append or replace the axios with newly available render method on Portkey Client SDK