Update int64 test to avoid warnings on MRI >= 2.4
Update int64 test to avoid warnings on MRI >= 2.4

estolfo/bson-ruby,estolfo/bson-ruby,estolfo/bson-ruby,mongodb/bson-ruby,mongodb/bson-ruby,ukblewis/bson-ruby,ukblewis/bson-ruby,ukblewis/bson-ruby,mongodb/bson-ruby,estolfo/bson-ruby,ukblewis/bson-ruby,mongodb/bson-ruby