ci: Run fourmolu - #101

The strategy configuration was canceled because "build._9_8_ubuntu-latest" failed

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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. For more information see: https://github.blog/changelog/2025-09-19-deprecation-of-node-20-on-github-actions-runners/

The import of ‘Data.List’ is redundant