cluster settings deprecation fix

[matthosking-mydeal]

Deprecation warning fix - move to aws_ecs_cluster_capacity_providers setting as inline is deprecated.

Types of changes

• [x] Bugfix (non-breaking change which fixes an issue)
• [ ] New feature (non-breaking change which adds functionality)
• [ ] Breaking change (fix or feature that would cause existing functionality to not work as expected)
• [ ] Documentation Update (if none of the other choices apply)

Checklist

• [x] I have read the CONTRIBUTING.md doc.
• [x] I have added necessary documentation (if appropriate).
• [x] Any dependent changes have been merged and published in downstream modules.