Reduce fragility of integration tests for explain by removing timing-dependent fields from the result document before comparing them.

Author: jyemin

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

@@ -948,6 +948,8 @@ class FindOperationSpecification extends OperationFunctionalSpecification {
     static BsonDocument sanitizeExplainResult(BsonDocument document) {
         document.remove('ok')
         document.remove('millis')
+        document.remove('executionStats')
+        document.remove('serverInfo')
         document
     }