tools: update ESLint to 5.15.0

Update ESLint to 5.15.0

PR-URL: https://github.com/nodejs/node/pull/26391


Reviewed-By: Rich Trott <rtrott@gmail.com>
Reviewed-By: Masashi Hirano <shisama07@gmail.com>
Reviewed-By: Ruben Bridgewater <ruben@bridgewater.de>