fix: refresh course structure on Android - #499

Node.js 20 is deprecated. The following actions target Node.js 20 but are being forced to run on Node.js 24: actions/cache@v3, actions/checkout@v3, actions/setup-java@v3, gradle/gradle-build-action@v2.6.1. For more information see: https://github.blog/changelog/2025-09-19-deprecation-of-node-20-on-github-actions-runners/

Failed to restore v8-gradle|Linux|test-tests[37a6259cc0c1dae299a7866489dff0bd]-c910f2473a0231cf283989342beb6662ed5e6265: Error: Cache service responded with 400