Removed unused using.

Author: papafe

tests/MongoDB.Driver.Tests/MongoClientSettingsTests.cs

@@ -28,7 +28,6 @@
 using MongoDB.Driver.Core.Connections;
 using MongoDB.Driver.Core.Servers;
 using MongoDB.Driver.Core.TestHelpers.XunitExtensions;
-using MongoDB.Driver.Encryption;
 using MongoDB.TestHelpers.XunitExtensions;
 using Moq;
 using Xunit;