Fix compilation errors resulting from merge.

Author: rstam

tests/MongoDB.Driver.Tests/ProjectionDefinitionBuilderTests.cs

@@ -18,8 +18,8 @@
 using MongoDB.Bson;
 using MongoDB.Bson.Serialization;
 using MongoDB.Bson.Serialization.Attributes;
-using MongoDB.Bson.TestHelpers.XunitExtensions;
 using MongoDB.Driver.Linq;
+using MongoDB.TestHelpers.XunitExtensions;
 using Xunit;
 
 namespace MongoDB.Driver.Tests

tests/MongoDB.Driver.Tests/Samples/AggregationSample.cs

@@ -17,9 +17,9 @@
 using System.Threading.Tasks;
 using FluentAssertions;
 using MongoDB.Bson.Serialization.Attributes;
-using MongoDB.Bson.TestHelpers.XunitExtensions;
 using MongoDB.Driver.Linq;
 using MongoDB.Driver.Tests.Linq.Linq3ImplementationTests;
+using MongoDB.TestHelpers.XunitExtensions;
 using Xunit;
 
 namespace MongoDB.Driver.Tests.Samples