CloudFormation Specifications
- Update CloudFormation specs to `169.0.0` (pull [3135](https://github.com/aws-cloudformation/cfn-lint/pull/3135))
- Support `db2-ae` and `db2-se` RDS engines for `AWS::RDS::DBInstance.Engine` (pull [3139](https://github.com/aws-cloudformation/cfn-lint/pull/3139))
Fixes
- Safely get `readOnlyProperties` (pull [3141](https://github.com/aws-cloudformation/cfn-lint/pull/3141))