add test: should not allow normalized balance to be zero

[significance]

      // it('should not allow normalized balance to be zero', async function () {
      //   await expect(
      //     postageStamp.createBatch(
      //       stamper,
      //       0,
      //       batch.depth,
      //       batch.bucketDepth,
      //       batch.nonce,
      //       batch.immutable
      //     )
      //   ).to.be.revertedWith('normalisedBalance cannot be zero');
      // });