If you set it up on your settings.json, you can update it there. If you stored your API Key in session you can run the command:
Open the command palette using: ctrl+shift+p
Run this command to reset your session: ChatGPT: Reset session
The next time you ask a question, it will ask you to enter your api key again. You can store it either in settings.json or in your session(Recommended)
If you set it up on your settings.json, you can update it there. If you stored your API Key in session you can run the command:
ctrl+shift+p
ChatGPT: Reset session