timers: add non-boolean ref test setImmediate

I added a test to improve the coverage here: https://github.com/nodejs/node/blob/bec918fb9bbf3fa1d8f9f5fcd37a9ee5f719dd63/lib/timers/promises.js#L96-L102

Checklist

• make -j4 test (UNIX), or vcbuild test (Windows) passes
• tests and/or benchmarks are included
• commit message follows commit guidelines