Upgrade AWS SDK Dependency to 3.7

Merge pull request #66 from bcuff/aws-upgrade

release 7.1.0 - aws dependency upgrade

Fix signing issue with other cultures

Details - #63

Resolve minor package restore warning

Details described here - #61

7.0.4

Improved credential and region resolution.

7.0.3

Added AwsHttpConnection constructor overload for AWSOptions

7.0.2

Fixed concurrency bug that will cause request signing to intermittently not happen. The bug was only on .NET Framework.

https://www.nuget.org/packages/Elasticsearch.Net.Aws/7.0.2