Blackened Chicken without lemon

1 tablespoon olive oil 1/3 cup chopped onion 1/3 cup chopped celery 1/3 cup chopped green bell pepper 1 tablespoon chopped fresh thyme 1 cup long-grain white[...]

1 teaspoon Hungarian sweet paprika 1 teaspoon freshly ground black pepper 1/2 teaspoon kosher salt 1/2 teaspoon garlic powder 1/2 teaspoon dried oregano 1/2[...]

4 (4-ounce) skinless, boneless chicken breast halves 2 teaspoons blackened steak seasoning (such as Paul Prudhomme's) Cooking spray 1 (10-ounce) package[...]