/etc/logcheck/ignore.d.server/arpwatch is in logcheck-database 1.3.17.
This file is owned by root:root, with mode 0o644.
The actual contents of the file can be viewed below.
1 2 | ^\w{3} [ :0-9]{11} [._[:alnum:]-]+ arpwatch: reused old ethernet address 0\.0\.0\.0 ([a-f0-9]{1,2}:){5}[a-f0-9]{1,2} \(([a-f0-9]{1,2}:){5}[a-f0-9]{1,2}\)$
^\w{3} [ :0-9]{11} [._[:alnum:]-]+ arpwatch: ethernet broadcast [0-9.]{7,15} 0:0:0:0:0:0$
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