Test: Remove unused import

Author: rozza

driver-core/src/test/functional/com/mongodb/operation/AggregateOperationSpecification.groovy

@@ -31,7 +31,6 @@ import com.mongodb.binding.ReadBinding
 import com.mongodb.client.model.Collation
 import com.mongodb.client.model.CreateCollectionOptions
 import com.mongodb.client.model.Filters
-import com.mongodb.client.test.CollectionHelper
 import com.mongodb.connection.AsyncConnection
 import com.mongodb.connection.ClusterId
 import com.mongodb.connection.Connection