misc(build): fix vercel deployment by adopting stricter engines grammar

[paulirish]

the vercel deployments broke because of #13099 👍

There's no formal spec for semver constraints, but the && syntax seems to be a problem. https://jubianchi.github.io/semver-check doesnt like it and neither does the semver npm package.

https://github.com/npm/node-semver#range-grammar wasn't mentioned in the grammar..

after looking at those docs for a bit i saw this example:

so anyway... its an easy fix and the new range is parsed happily by 'semver' and vercel's thing.

[connorjclark]

loose is a thing in semver which seems to ignore unknown characters (like &&...). Since ignoring && results in treating that token like a space, which is how semver apparently does logical AND, it resulted in this constraint working OK when loose === true. That's the default in yarn, which is why my manual testing switching node versions seemed to check out.