Update pysr requirement from <=1.5.10,>=1.5.0 to >=1.5.0,<=2.0.0 - #64

Node.js 20 is deprecated. The following actions target Node.js 20 but are being forced to run on Node.js 24: actions/cache@v4. For more information see: https://github.blog/changelog/2025-09-19-deprecation-of-node-20-on-github-actions-runners/