By David Shepardson WASHINGTON (Reuters) -Stellantis unit FCA US will pay $5.6 million to resolve a California investigation into violations of air quality regulations, the state said on Thursday. The California Air Resources Board (CARB) said the 30,600 vehicles involved in the settlement include 2012-2018 model year Ram 1500, Jeep Grand Cherokee and Dodge Durango vehicles that were equipped with 5.7L gasoline engines and did not comply with certification emission standards. FCA will pay a $2.8 million civil penalty and $2.8 million to bring more electric school buses to schools in the South …