ATLANTA — Georgia’s governor on Wednesday criticized the “unbecoming squabble” that has engulfed the state Capitol since fellow Republicans threatened to punish Delta Air Lines for cutting business ties with the National Rifle Association. Gov. Nathan Deal, serving his final year in office, broke his silence on the controversy during a news conference with an apparent jab at candidates running to succeed him. He said a tax overhaul bill caught up in the debate had been “put at risk by the types of antics that tend to plague election years.”