What does Huck do at the end of this chapter that was surprising in the historical and social context of the book? Why is this a turning point for Huck and Jim's friendship?

"This is in reference to Huck's trick on Jim over Jim thinking he had a dream. Huck realizes his trick was a mean one. He works himself up to go apologize, which he finds particularly difficult to do because Jim is black. Still, he says, he’s glad he did. During this era, white people did not apologize to black people for anything. Huck's apology was both heartfelt and an acknowledgement that they are equals of sorts."