fix: comment result of average() function

[okinawaa]

Thank you for providing a good library.
There was a difference between the test code and the actual annotation, so I fixed it.

average docs

// average.spec.ts

 it.each([
      [[1, 2, 3, 4, 5], 3],
      [[], NaN],
    ])(
      "should return the average of the given elements",
      function (nums, result) {
        expect(average(nums)).toEqual(result);
      },
    );

    it("should be able to be used as a curried function in the pipeline", function () {
      const res = pipe([1, 2, 3, 4, 5], average);
      expect(res).toEqual(3);
    });

Thank you😎

[ppeeou]

Thank you for your contribution :) 👍