No. Not true in any practical sense. For two randomly selected people, one atheist and the other religious, the odds of the atheist having a higher IQ might be 55/45 instead of 50/50. A few points of IQ doesn’t amount to any practical difference for the average encounter. There are smart people on both sides of the fence.
IQ scores aren’t really a very good measure of cognitive ability beyond analytical thinking, and tend to have many biases.