Update github actions

[flabbamann]

Update github actions:

• checkout@v5
• setup-python@v6

Both update the used node version from 20 to 24 as node 20 is deprecated on github action runners: https://github.blog/changelog/2025-09-19-deprecation-of-node-20-on-github-actions-runners/

[coveralls]

coverage: 96.875%. remained the same
when pulling 3181d82 on flabbamann:actions
into cb8283b on hthiery:master.