Can my diet in pregnancy have an impact on my child's food preferences?

No. There's no data to allow one to answer this question. On the other hand, logical thinking would lead one to conclude that there's no way the fetus would "know" what you are eating. The placenta, which is the interface between mother and baby, only transfers fundamental nutrients like Amino Acids and glucose; not "broccoli flavor molecules.".
No. There's no data to suggest this is true.