Add keymanager-aws version as exported from dependencyManagement of parent

[ALRubinger]

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.