Perfectly fine, in everyday usage, to put “that” there or leave it out. You’d have to really be a precise grammarian to think otherwise. Both forms are commonly used and mean exactly the same thing.

More information here: https://www.ef.com/ca/english-resources/english-grammar/defining-relative-clauses/ [excerpt] INCLUDING OR OMITTING THE RELATIVE PRONOUN The relative pronoun can only be omitted when it is the object of the clause. When the relative pronoun is the subject of the clause, it cannot be omitted.

Hi, you question is well answered below, I see this happens in Spanish sometimes, it seems to be a way of saying what you want to say using as few words as possible, you could actually remove "The" also from the sentence and be saying the same thing!