fix: skip spotbugs upload step if not coming from eclipse-mat repo - #195

Node.js 20 is deprecated. The following actions target Node.js 20 but are being forced to run on Node.js 24: actions/checkout@v4, actions/setup-java@v4, lcollins/spotbugs-github-action@v3.2.0. For more information see: https://github.blog/changelog/2025-09-19-deprecation-of-node-20-on-github-actions-runners/