Update CodeBuild Containers used to aws/codebuild/standard:6.0

[stefanfreitag]

This is a follow-up of #641.

Current situation

With the release of https://github.com/awslabs/aws-service-catalog-puppet/releases/tag/0.223.0 the code build image version was changed from 4.0 to 5.0.
In the last days I saw messages that also version 5.0 enters unsupported mode on March 30, 2023. For example, this was mentioned in the AWS CDK project and confirmed by an AWS TAM.

Proposed solution

Upgrade to standard image version 6.0

I could come up with a PR in the next days - please let me know if that would be fine for you.

[mpratsch]

FYI: I tried the initializer template and deployed that with the 6.0 version but it requires python 3.10 therefore it failed since SCT uses python 3.9 at the moment.