MNT: checkout v3

[kmuehlbauer]

see actions/checkout#1590 and https://github.com/openradar/erad2022/actions/runs/7970881407/job/21760007234

Run actions/checkout@v4
/usr/bin/docker exec ecf8b7c89a935d27067213571f6817cfde75c0635fc33811b9a7d4db0d06301e sh -c "cat /etc/*release | grep ^ID"
/__e/node20/bin/node: /lib/x86_64-linux-gnu/libc.so.6: version `GLIBC_2.28' not found (required by /__e/node20/bin/node)

[github-actions]

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[kmuehlbauer]

setting v3 seems to fix that issue, going to merge.