Hi!
In that sentence, refute is the correct word.
However, refute and disprove are very similar.
Disprove only means to prove that something is wrong by using evidence.
Refute has 2 meanings though; 1. is the same exact same as disprove, and 2. means to deny or contradict a statement.
So in the sentence "the scientists refuted the superstition that black cats bring bad luck", they are only denying (disagreeing) that black cats bring bad luck. There is no evidence or proof, just their opinion, so disprove cannot work here.
Hope this helps!