Set logging level to INFO, was overridden by newer TF (#3358)

ml-agents/mlagents/trainers/learn.py

         trainer_logger.setLevel("DEBUG")
         env_logger.setLevel("DEBUG")
     else:
+        trainer_logger.setLevel("INFO")
+        env_logger.setLevel("INFO")
         # disable noisy warnings from tensorflow.
         tf_utils.set_warnings_enabled(False)