Apple will bring back the fourth-generation iPad on Tuesday, 9to5Mac reports. According to a source, Apple stores have been receiving shipments of the previously discontinued iPad. Both Wi-Fi and LTE black and white 16GB models have arrived in stores. It’s likely that Apple will make the 16GB fourth-gen iPad the low-end $399 iPad model, and discontinue the second-generation iPad, so all current iPads would be Lightning devices. It was reported…