CSHARP-1834: Fix a test that was using too small a value for MaxStaleness.

Author: rstam

tests/MongoDB.Driver.Core.Tests/Core/Operations/FindOperationTests.cs

@@ -427,7 +427,7 @@ public void Execute_should_find_all_the_documents_matching_the_query_when_max_st
             RequireServer.Check().Supports(Feature.MaxStaleness);
             EnsureTestData();
             var subject = new FindOperation<BsonDocument>(_collectionNamespace, BsonDocumentSerializer.Instance, _messageEncoderSettings);
-            var readPreference = new ReadPreference(ReadPreferenceMode.SecondaryPreferred, maxStaleness: TimeSpan.FromSeconds(30));
+            var readPreference = new ReadPreference(ReadPreferenceMode.SecondaryPreferred, maxStaleness: TimeSpan.FromSeconds(90));
 
             // the count could be short temporarily until replication catches up
             List<BsonDocument> result = null;