chore: update archive/github-actions-slack action to v2.11.0 - #666

Node.js 20 is deprecated. The following actions target Node.js 20 but are being forced to run on Node.js 24: actions/checkout@ee0669bd1cc54295c223e0bb666b733df41de1c5, actions/setup-node@7c12f8017d5436eb855f1ed4399f037a36fbd9e8. For more information see: https://github.blog/changelog/2025-09-19-deprecation-of-node-20-on-github-actions-runners/