Remove unused usings

Author: adams85

source/FileLogger/LogFileSettings.cs

@@ -2,7 +2,6 @@
 using System.Collections.Concurrent;
 using System.Collections.Generic;
 using System.Diagnostics.CodeAnalysis;
-using System.Linq;
 using System.Reflection;
 using System.Text;
 using System.Threading;

test/FileLogger.Test/Helpers/PlatformFactAttribute.cs

@@ -1,5 +1,4 @@
 using System;
-using System.Linq;
 using System.Runtime.InteropServices;
 using Xunit;