It's all about clauses and relative pronouns.
In a defining clause (ie: one not wrapped in commas, where the information is essential to understanding the sentence), as in the case here, Noel was free to chose his relative pronoun. In more formal prose it would be advised to stick to the specific pronoun. If the subject and object were different he could have omitted the pronoun altogether.
Were the line to contain a non-defining clause (ie: on which contains additional information about the subject) he would have to chose the correct pronoun for the subject.
ie: Maybe, you're the one that's gonna save me
or Maybe, you're the one who's gonna save me.
Maybe, you're the one who/that I'll save
Maybe, you're the one I'll save
Maybe, that girl, who is wearing pink, is gonna save me. (no option for 'that')