Bump Ruby to version 2.3.7 and 2.6.1

[real-mj-song]

https://docs.aws.amazon.com/opsworks/latest/userguide/workingcookbook-ruby.html

OpsWorks Chef 11.10 officially supports Ruby 2.6.1 (since agent version 3451) and 2.3.7 (since agent version 3448)

• Bump 2.3.x default Ruby version to 2.3.7.
• Support Ruby 2.6.1

[real-mj-song]

Seems like the following commits are pushed for newer ruby version support. Closing this issue. https://github.com/aws/opsworks-cookbooks/commit/10b912675798d62b4032ff195d56df83ba81cf5a https://github.com/aws/opsworks-cookbooks/commit/4028e637aadd2fcaadd46de3dfbe49a025681f2b