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
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make -j4 test
(UNIX), orvcbuild test
(Windows) passes -
tests and/or benchmarks are included -
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