Jest, console.warn require.cache modification is not permitted

[danielweck]

Due to this: https://github.com/facebook/jest/pull/9841/files and this: https://github.com/sindresorhus/conf/blob/410cc144141f1467cc91fe4b16f6b7f42a8afac8/index.js#L21-L23 =>

console.warn
    `require.cache` modification is not permitted

(output'ed many times in the console when unit-testing, with full stacktrace, so quite disruptive, albeit non-fatal unless unit-tests check for CLI output)