cleaned up sampler

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

 using System;
-using System.Linq;
-using Unity.MLAgents;
-using UnityEngine;
 
 namespace Unity.MLAgents
 {
 
         public Func<float> CreateUniformSampler(float min, float max, int seed)
         {
-            System.Random distr = new System.Random(seed);
+            Random distr = new Random(seed);
             return () => min + (float)distr.NextDouble() * (max - min);
         }
 
         public Func<float> CreateMultiRangeUniformSampler(IList<float> intervals, int seed)
         {
             //RNG
-            System.Random distr = new System.Random(seed);
+            Random distr = new Random(seed);
-            int numIntervals = (int)(intervals.Count()/2);
+            int numIntervals = (int)(intervals.Count/2);
             // List that will store interval lengths
             float[] intervalSizes = new float[numIntervals];
             // List that will store uniform distributions
             for(int i = 0; i < numIntervals; i++)
             {
-                var min = intervals.ElementAt(2 * i);
-                var max = intervals.ElementAt(2 * i + 1);
+                var min = intervals[2 * i];
+                var max = intervals[2 * i + 1];
                 var intervalSize = max - min;
                 sumIntervalSizes += intervalSize;
                 intervalSizes[i] = intervalSize;