Pico-8 defines these keys and I think you can change them in one of the config files but am unsure which. I always played 2 player with connected controllers for this very reason.
Hi, I just downloaded the Windows version and there doesn't appear to be an easy way to do this (no config file). If you have a purchased version of pico 8 installed, you can use the KEYCONGIF utility (apparently): https://pico-8.fandom.com/wiki/Keyconfig
No idea how you'd do it if running the executables though without downloading a third-party application to do this - suggest you're very careful if you have to go this route though.