[doc] wrong path to cucumber in the .gif example

[Sébastien Fournier]

Binary "/node_modules/.bin/cucumber.js" doesn't exists anymore as cucumber-js v4, see https://github.com/cucumber/cucumber-js/blob/master/CHANGELOG.md

[Ilya Kozhevnikov]

It is meant for illustration purposes only, not as documentation. I rerecord it whenever pretty output changes significantly.