Remove import.

Author: surfnerd

com.unity.ml-agents/Runtime/Agent.cs

@@ -1,7 +1,6 @@
 using System;
 using System.Collections.Generic;
 using System.Collections.ObjectModel;
-using System.Linq;
 using UnityEngine;
 using Unity.Barracuda;
 using Unity.MLAgents.Actuators;