openbsd ci: try to remove more temporary files

[sylvestre]

No description provided.

[oech3]

vmactions/openbsd-vm@v1 might have some config to change size of VM image.

[github-actions]

GNU testsuite comparison:

Note: The gnu test tests/id/smack was skipped on 'main' but is now failing.
Note: The gnu test tests/mkdir/smack-no-root was skipped on 'main' but is now failing.
Note: The gnu test tests/mkdir/smack-root was skipped on 'main' but is now failing.

[oech3]

Passed

[sylvestre]

ok, auto merge to finally have green builds again

[oech3]

I think result of df -h is not shown https://github.com/uutils/coreutils/actions/runs/20571918319/job/59080715573?pr=9899#step:3:8