[Dependency Upgrade] Bump org.apache.rat:apache-rat from 0.15 to 0.16.1 (or later) in /buildSrc

Is your feature request related to a problem? Please describe

https://github.com/opensearch-project/OpenSearch/pull/12058

dependabot can't upgrade this dependency since upgrading this library requires class path changes & maybe some refactoring.

Creating the issue so that someone (good first issue) can evaluate the class path changes or any concerns with upgrading this dependency.

Describe the solution you'd like

Look for failing class path resolutions, find alternatives or replaced classes in upgraded version.

Related component

Build

Describe alternatives you've considered

No response

Additional context

No response