github copilot extension

No, I don't think you can.

Cloud9 is integrated with CodeWhisperer which is a machine learning powered service that helps improve developer productivity by generating code recommendations based on developers’ comments in natural language and their code in the IDE. Currently CodeWhisperer is available for the Java, JavaScript, Python, C# and TypeScript programming languages

https://docs.aws.amazon.com/cloud9/latest/user-guide/codewhisperer.html