TAMPA, Fla—With the clock ticking on their time together, the defending champion Tampa Bay Lightning talked about what they already knew was their last Stanley Cup run as a group. They talked about it midway through the playoffs. They talked about it on the verge of reaching the final. Changes were coming, so captain Steven Stamkos and his teammates told each other, “Let’s take advantage of this opportunity.” Tampa Bay did just that in winning the championship back to back, and players and coaches celebrated in a fashion befitting the end of an era. Coach Jon Cooper said it felt like “the last day of school” and the Lightning aced their final exam before inevitable changes break them apart. “This team, knowing that we’re probably not going to be together, this was the end of a special group for two years,” Cooper said. “Who knows what’s going to happen here, …