Bug: Spurious date check

[sebbASF]

The code at https://github.com/apache/incubator-ponymail/blob/a65a09cceb17ce6877097856ae437ac977d00902/tools/list-lists.py#L67

checks whether the date of the entry is less than 2 days in the future.

There does not seem to be any reason for this. Either the reason should be documented, or the check should be dropped.