Nuke inaccurate callback-may-error comment

I mean it's correct in that the callback can error, but such an event no
longer bubbles its way back to the caller.

AceComm-3.0/ChatThrottleLib.lua

@@ -521,7 +521,7 @@ function ChatThrottleLib:SendChatMessage(prio, prefix,   text, chattype, languag
 		if callbackFn then
 			securecallfunction(callbackFn, callbackArg, true, SendAddonMessageResult.Success)
 		end
-		-- USER CALLBACK MAY ERROR
+
 		return
 	end