Removed enable monitoring in engine (GcStats handles it).

src/BenchmarkDotNet/Engines/Engine.cs

@@ -216,11 +216,6 @@ private ClockSpan Measure(Action<long> action, long invokeCount)
         [MethodImpl(CodeGenHelper.AggressiveOptimizationOption)]
         private (GcStats, ThreadingStats, double) GetExtraStats(IterationData data)
         {
-            // we enable monitoring after main target run, for this single iteration which is executed at the end
-            // so even if we enable AppDomain monitoring in separate process
-            // it does not matter, because we have already obtained the results!
-            EnableMonitoring();
-
             // Warm up the GetAllocatedBytes function before starting the actual measurement.
             DeadCodeEliminationHelper.KeepAliveWithoutBoxing(GcStats.ReadInitial());
 
@@ -285,15 +280,6 @@ internal static void ForceGcCollect()
 
         public void WriteLine() => Host.WriteLine();
 
-        private static void EnableMonitoring()
-        {
-            if (RuntimeInformation.IsOldMono) // Monitoring is not available in Mono, see http://stackoverflow.com/questions/40234948/how-to-get-the-number-of-allocated-bytes-in-mono
-                return;
-
-            if (RuntimeInformation.IsFullFramework)
-                AppDomain.MonitoringIsEnabled = true;
-        }
-
         [UsedImplicitly]
         public static class Signals
         {