Rewinder - remove message callback, I dont' think this message is worth the code, especially since mainform always adds a message

src/BizHawk.Client.Common/rewind/Rewinder.cs

@@ -19,8 +19,6 @@ namespace BizHawk.Client.Common
 		private bool _lastRewindLoadedState;
 		private byte[] _deltaBuffer = new byte[0];
 
-		public Action<string> MessageCallback { get; set; }
-
 		public bool RewindActive => RewindEnabled && !SuspendRewind;
 
 		private bool RewindEnabled { get; set; }
@@ -61,10 +59,6 @@ namespace BizHawk.Client.Common
 				RewindFrequency = rewindConfig.FrequencySmall;
 			}
 
-			MessageCallback?.Invoke(RewindEnabled ?
-				$"Rewind enabled, frequency: {RewindFrequency}" :
-				"Rewind disabled");
-
 			_rewindDeltaEnable = rewindConfig.UseDelta;
 
 			if (RewindActive)

src/BizHawk.Client.EmuHawk/MainForm.cs

@@ -200,10 +200,7 @@ namespace BizHawk.Client.EmuHawk
 			}
 
 			GlobalWin.MainForm = this;
-			Rewinder = new Rewinder
-			{
-				MessageCallback = AddOnScreenMessage
-			};
+			Rewinder = new Rewinder();
 
 			Global.InputManager.ControllerInputCoalescer = new ControllerInputCoalescer();
 			Global.FirmwareManager = new FirmwareManager();