Pry.config.prompt is deprecated

[a2ikm]

Pry.config.prompt used here is deprecated since pry 0.13.0. https://github.com/pry/pry/blob/5805952cf32f320508df6a5ba4f768b9f4394805/CHANGELOG.md?plain=1#L114-L120

pry with marco-polo now prints the following warning:

warning: setting prompt with help of `Pry.config.prompt = [proc {}, proc {}]` is deprecated. Use Pry::Prompt API instead

[sakuro]

I'd submitted a PR for that https://github.com/arches/marco-polo/pull/16 but this repo seems inactive for years 🤷🏽