Scribe 2 of 𝓟 initially wrote those that; but before crossing the t’s for that, he deleted the that and then wrote inline the alternative relative pronoun which. This immediate correction is undoubtedly the reading of the original manuscript. Both readings are possible for the Book of Mormon. For a similar example of a mix-up between the relative pronouns which and that (but in Oliver Cowdery’s copywork), see under Mosiah 5:6. For more general discussion, see under which in volume 3.
Summary: Accept scribe 2’s immediate correction of that to which in 𝓟; since either reading is possible, the corrected reading in 𝓟 is undoubtedly the reading of the original manuscript.