How long has he been going to the gifted pull-out? For a few weeks or months, or since September?
Usually there is something else underneath the "boredom" issue, so I agree with the other posters that it is worth looking into. But I think Nautigal is right that it just may not be all that great as a program (as he ever expressed enthusiasm for it?).
Could the fact his friend is autistic be causing the other kids to tease or avoid him? I would definitely talk to the teacher, but I would not say that he says he is bored, but say that he is expressing disinterest and you are wondering if she has noticed any social/learning dynamics that could be contributing.
Good luck, Cat