Apologies for my OT response. I goofed reading the details before my 1st cup of coffee.
To your question my colleague and I were discussing this earlier today. Presently we are not aware of a technique to constrain GitHub Copilot to generate suggestions compatible for a specific Java version. We have a couple of ideas that we hope to test out in the next few days. We will post any successes we have and additional suggestions as we learn more.
Again apologies for my initial goof response.
W