fix: Clear the timer for task timeout after the task has completed

[katsuya]

The timer for task timeout is not cleared with clearTimeout, causing it to persist in the event loop even after the task has finished processing. As a result, the Node.js process cannot terminate until the time specified for the timer has elapsed. The issue can be replicated using the following code:

 await PromisePool.for([...Array(100).keys()])
    .withConcurrency(100)
    .withTaskTimeout(180 * 1000)
    .process(async (key, _index, _pool) => {
      return key
    })

const info = process.getActiveResourcesInfo()
console.log({ info })

[marcuspoehls]

@katsuya Hey Katsuya, good catch! Thank you for the pull request 😊 I'll merge it today and publish a new release

[marcuspoehls]

@katsuya I’ve published version 3.1.0 containing your timer improvements. Thank you!