[skip ci] minor formatting change

ml-agents/mlagents/trainers/optimizer/tf_optimizer.py

 
         if hvd is not None:
             adam_optimizer = tf.train.AdamOptimizer(
-                learning_rate=learning_rate, name=name)
+                learning_rate=learning_rate, name=name
+            )
             horovod_optimizer = hvd.DistributedOptimizer(adam_optimizer)
         else:
             adam_optimizer = tf.train.AdamOptimizer(