[202x][unroll] Only run the default LLVM loop unroll for 202x onward - #8822

Node.js 20 is deprecated. The following actions target Node.js 20 but are being forced to run on Node.js 24: actions/checkout@11bd71901bbe5b1630ceea73d27597364c9af683, actions/setup-python@7f4fc3e22c37d6ff65e88745f38bd3157c663f7c, step-security/changed-files@3dbe17c78367e7d60f00d78ae6781a35be47b4a1. For more information see: https://github.blog/changelog/2025-09-19-deprecation-of-node-20-on-github-actions-runners/