Update AWS API version

Summary: This updates the AWS API date to a newer version, which means AWS will expose more functionality in responses and requests to their REST API.

Test Plan: Encountered a problem where properties weren't available in the response during Drydock EC2 allocation because of this old version; updated this version and the properties started appearing.

Reviewers: epriestley, #blessed_reviewers

Reviewed By: epriestley, #blessed_reviewers

Subscribers: epriestley, Korvin

Differential Revision: https://secure.phabricator.com/D10545