Bump Rancher version to v2.13.8 - #636

Node.js 20 is deprecated. The following actions target Node.js 20 but are being forced to run on Node.js 24: actions/checkout@f43a0e5ff2bd294095638e18286ca9a3d1956744, actions/setup-go@d35c59abb061a4a6fb18e82ac0862c26744d6ab5, docker/build-push-action@ca052bb54ab0790a636c9b5f226502c73d547a25, golangci/golangci-lint-action@4afd733a84b1f43292c63897423277bb7f4313a9. For more information see: https://github.blog/changelog/2025-09-19-deprecation-of-node-20-on-github-actions-runners/