Update CHANGELOG.md

Co-authored-by: Josh Cooper <737664+joshcooper@users.noreply.github.com>

Author: david22swan

CHANGELOG.md

@@ -5,7 +5,7 @@ All significant changes to this repo will be summarized in this file.
 
 ## [1.9.0](https://github.com/puppetlabs/puppet-resource_api/tree/1.9.0) (2023-08-08)
 
-[Full Changelog](https://github.com/puppetlabs/puppet-resource_api/compare/1.8.18...1.8.18)
+[Full Changelog](https://github.com/puppetlabs/puppet-resource_api/compare/1.8.18...1.9.0)
 
 **Implemented enhancements:**