Allow use of async return value promise

[NilSet]

I want to report a bug.

SonarJS version: 3.1.1

Rule key: S3699 aka UseOfEmptyReturnValue

Reproducer

var arrowReturnsPromise = async () => {
   var x = () => {return 1}
};
x = arrowReturnsPromise(); // False-positive

Expected behavior
All async functions return a promise, regardless of if the body has an empty return value, so this rule should allow use of the return value.