tools: enforce arrow function brace usage linting
Checklist
-
tests and code linting passes -
the commit message follows commit guidelines
Affected core subsystem(s)
tools test lib
Description of change
Enable linting such that if braces are not required for an arrow function body, omit them.
Refs: https://github.com/nodejs/node/pull/6390#discussion-diff-61484591 (where there was a nit about this and I'd rather tools tell me code style nits rather than people...)
/cc @bnoordhuis