Fix singularity ci tests - #245

Node.js 20 is deprecated. The following actions target Node.js 20 but are being forced to run on Node.js 24: nichmor/minimal-read-yaml@1f7205277e25e156e1f63815781db80a6d490b8f. For more information see: https://github.blog/changelog/2025-09-19-deprecation-of-node-20-on-github-actions-runners/