docs: improve promise terminology

This is kind of a nit but:

A promise is:

• resolved if its fate is known either because it is tracking another promise or because it is fulfilled with a value. For example const p = Promise.resolve(timersPromises.setTimeout(1000)); - here p is a resolved promise. The promise constructor calls its executor argument function resolve for this case since it performs resolution and you can pass it a promise and it'll track it.
• fulfilled means what the docs mean when they use "resolved". It means "this promise has settled on a value successfully". p for the example above has not fulfilled (immediately).