Cleanup a stale comment and move the reflection using statement into the .NET backend support location.

Author: wiwei

Assets/MixedRealityToolkit/Attributes/MixedRealityControllerAttribute.cs

@@ -5,9 +5,9 @@
 using Microsoft.MixedReality.Toolkit.Core.Definitions.Utilities;
 using System;
 using System.Linq;
-using System.Reflection;
 
 #if WINDOWS_UWP && !ENABLE_IL2CPP
+using System.Reflection;
 using Microsoft.MixedReality.Toolkit.Core.Extensions;
 #endif // WINDOWS_UWP && !ENABLE_IL2CPP
 
@@ -61,9 +61,6 @@ public MixedRealityControllerAttribute(
         /// <summary>
         /// Convenience function for retrieving the attribute given a certain class type.
         /// </summary>
-        /// <remarks>
-        /// This function is only available in a UnityEditor context.
-        /// </remarks>
         public static MixedRealityControllerAttribute Find(Type type)
         {
 #if WINDOWS_UWP && !ENABLE_IL2CPP