ci: Bump actions/upload-artifact from 4 to 6#15

dependabot[bot] wants to merge 1 commit intomaincachekit-io/cachekit-core:mainfrom

dependabot/github_actions/actions/upload-artifact-6cachekit-io/cachekit-core:dependabot/github_actions/actions/upload-artifact-6Copy head branch name to clipboard