tests/vm: update openbsd image to 7.6

tests/vm: update openbsd image to 7.6

Remove tomli as Python has been updated to 3.11.

[thuth: The "Time appears wrong" line is now necessary since the server
 seems to provide a wrong timestamp. We likely have to remove that again
 later once the server is running with the correct time again]

Signed-off-by: Brad Smith <brad@comstyle.com>
Reviewed-by: Thomas Huth <thuth@redhat.com>
Tested-by: Thomas Huth <thuth@redhat.com>
Message-ID: <ZwtmfVlWgFRF9G8W@humpty.home.comstyle.com>
Signed-off-by: Thomas Huth <thuth@redhat.com>