Add `keymanager-aws` version as exported from dependencyManagement of `parent`

Consumers of `tbdex-kt` get `web5-kt` transitively, and are not making explicit version declarations for `web5-kt`. When they want to add the extension module `aws-keymanager`, this means they'll have to manually add the version they want to consume. Make it so we're exporting the version of the `aws-keymanager` even if we're not exporting the dep itself as part of the `distribution`.