remove unused using directives

Author: adelinowona

tests/MongoDB.Driver.Tests/Search/AtlasSearchTests.cs

@@ -16,15 +16,12 @@
 using System;
 using System.Collections.Generic;
 using System.Linq;
-using System.Threading;
 using FluentAssertions;
 using MongoDB.Bson;
 using MongoDB.Bson.Serialization.Attributes;
-using MongoDB.Driver.Core.Misc;
 using MongoDB.Driver.Core.TestHelpers.Logging;
 using MongoDB.Driver.GeoJsonObjectModel;
 using MongoDB.Driver.Search;
-using MongoDB.TestHelpers.XunitExtensions;
 using Xunit;
 using Xunit.Abstractions;
 using Builders = MongoDB.Driver.Builders<MongoDB.Driver.Tests.Search.AtlasSearchTests.HistoricalDocument>;