tools: update ESLint to 6.6.0

Update ESLint to 6.6.0

PR-URL: https://github.com/nodejs/node/pull/30123


Reviewed-By: Luigi Pinca <luigipinca@gmail.com>
Reviewed-By: Rich Trott <rtrott@gmail.com>
Reviewed-By: Yongsheng Zhang <zyszys98@gmail.com>
Reviewed-By: Trivikram Kamat <trivikr.dev@gmail.com>