Find the pip conf file, and then remove the last few lines which are a section containing a variable set to 'content-addressable-pool'.
The pip config unset ... command will probably also work but I haven’t tried it before.
avoid upgrading pip even if it tells you to. As long as your repls use nix modules config (I see that they do), any updates that you need will come automatically. Running this in Shell forces an update (as does making a change to .replit in the IDE):