Bump julia-actions/julia-downgrade-compat from 2 to 2.6.2 in the all-github-actions group - #132

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