Remove references to batcher in comments. (#2701)

UnitySDK/Assets/ML-Agents/Scripts/Grpc/RpcCommunicator.cs

         Dictionary<string, bool> m_HasData =
             new Dictionary<string, bool>();
 
-        /// Keeps track of which brains queried the batcher on the current step
+        /// Keeps track of which brains queried the communicator on the current step
         Dictionary<string, bool> m_HasQueried =
             new Dictionary<string, bool>();
 
 
-        /// The current UnityRLOutput to be sent when all the brains queried the batcher
+        /// The current UnityRLOutput to be sent when all the brains queried the communicator
         UnityRLOutputProto m_CurrentUnityRlOutput =
             new UnityRLOutputProto();
 

UnitySDK/Assets/ML-Agents/Scripts/ICommunicator.cs

         /// Sends the observations. If at least one brain has an agent in need of
         /// a decision or if the academy is done, the data is sent via
         /// Communicator. Else, a new step is realized. The data can only be
-        /// sent once all the brains that subscribed to the batcher have tried
+        /// sent once all the brains that were part of initialization have tried
         /// to send information.
         /// </summary>
         /// <param name="key">Batch Key.</param>

UnitySDK/Assets/ML-Agents/Scripts/LearningBrain.cs

         protected ICommunicator m_Communicator;
 
         /// <summary>
-        /// Sets the Communicator of the Brain. The brain will call the communicator at every step and give
+        /// Sets the ICommunicator of the Brain. The brain will call the communicator at every step and give
         /// it the agent's data using PutObservations at each DecideAction call.
         /// </summary>
         /// <param name="communicator"> The Batcher the brain will use for the current session</param>