Bill Tindall, E.Tn.
The deposit is calcium carbonate. Any acid will dissolve it. The product mentioned is lactic acid. I don't know any reason that lactic acid would be better than acetic acid except it will stink less and may dissolve iron stain better. There is no reason to dilute white vinegar which is chemically pure acetic acid. Citric acid will work too, probably a bit better in that it may work quicker for some complicated chemical reasons.