Fix FP S3699 (no-use-of-empty-return-value): Ignore ambient functions

[yassin-kammoun-sonarsource]

The rule is reporting false positives on TypeScript ambient functions:

declare function foo(bar: number): number;
let x = foo(42); // False positive

https://community.sonarsource.com/t/typescript-false-positive-for-typescript-s3699-when-using-declare-function/109601