Chore: update go sdk generator version - #295

Node.js 20 is deprecated. The following actions target Node.js 20 but are being forced to run on Node.js 24: actions/setup-go@v5, actions/setup-java@v4. For more information see: https://github.blog/changelog/2025-09-19-deprecation-of-node-20-on-github-actions-runners/

Restore cache failed: Dependencies file is not found in /home/runner/work/stackit-sdk-generator/stackit-sdk-generator. Supported file pattern: go.sum