Pin OpenSSL below 4 to fix nightly conan builds - #843

Node.js 20 is deprecated. The following actions target Node.js 20 but are being forced to run on Node.js 24: actions/checkout@ac593985615ec2ede58e132d2e21d2b1cbd6127c. For more information see: https://github.blog/changelog/2025-09-19-deprecation-of-node-20-on-github-actions-runners/