Security update eslint to >= 6.2.1 or eslint-util >= 1.4.1

https://github.com/mysticatea/eslint-utils/security/advisories/GHSA-3gx7-xhv7-5mx3 says:

'getStaticValue' function can execute arbitrary code

This can be fixed by updating eslint to >= 6.2.1 or updating eslint-util to >= 1.4.1.