Pretty sure they used an I, not an A. Their way of "getting around" it wasn't even to say "nagger", it was to write the word as-is but cut off the bottom half of the letters (it was the last word in the bubble) so they could go "oh teehee, you thought I wrote that? Maybe those were C's, not G's, maybe you're the true racist for filling in the blanks :3c" or something equally asinine.
They did end up editing the chapter though, which makes talking about it kind of obnoxious because not everyone actually saw what was being complained about before they got nuked.
edit: I actually went and found the credits page in question, and it's cut off enough that it could be either an I or an A, but considering the "joke" on the page it's extremely obvious what it's supposed to say and "nagger" wouldn't make a single bit of sense unless you're really stupid enough to believe people aren't capable of context clues.