Issue on docs

[tombeckenham]

Path: /workflow/troubleshooting/general

You should mention that this problem can easily be caused by workflows with a single parallel operation like:

    const listOfItems = await Promise.all(
      input.inputList.map(async (item, index) => {
        return await context.run(`some-step-${index}`, async () => {
          //  ... do something with the item
          return item;
        });
      })
    );

It took me a long time to work out that if the inputList is empty, the workflow fails with an authentication error. It didn't appear that I was doing anything non-idempotent outside of the workflow steps