chore: prepare 6.8.1 release (#268)

Author: kangasta

CHANGELOG.md

@@ -5,6 +5,7 @@ See updating [Changelog example here](https://keepachangelog.com/en/1.0.0/)
 
 ## [Unreleased]
 
+## [6.8.1]
 ### Changed
 - kubernetes: `WaitForKubernetesClusterState` ignores two first 404 responses to avoid errors caused by possible false _not found_ responses right after cluster has been created.
 
@@ -351,7 +352,8 @@ See updating [Changelog example here](https://keepachangelog.com/en/1.0.0/)
 
 First stable release
 
-[Unreleased]: https://github.com/UpCloudLtd/upcloud-go-api/compare/v6.8.0...HEAD
+[Unreleased]: https://github.com/UpCloudLtd/upcloud-go-api/compare/v6.8.1...HEAD
+[6.8.1]: https://github.com/UpCloudLtd/upcloud-go-api/compare/v6.8.0...v6.8.1
 [6.8.0]: https://github.com/UpCloudLtd/upcloud-go-api/compare/v6.7.1...v6.8.0
 [6.7.1]: https://github.com/UpCloudLtd/upcloud-go-api/compare/v6.7.0...v6.7.1
 [6.7.0]: https://github.com/UpCloudLtd/upcloud-go-api/compare/v6.6.0...v6.7.0