[SKIP SOF-TEST] .github/zephyr: upgrade obsolete actions/setup-python@v4 to v5

[marc-hb]

Fixes the following warning: https://github.com/thesofproject/sof/actions/runs/8289483047

Node.js 16 actions are deprecated. Please update the following actions
to use Node.js 20: actions/setup-python@v4. For more information see:
https://github.blog/changelog/2023-09-22-github-actions-transitioning-from-node-16-to-node-20/.