Update to 6.06

UPstream changes:
6.06      2023-07-06 22:29:55Z
    - Use copyright year rather than range (GH#18) (Olaf Alders)
    - Replace "Test" with "Test::More" (GH#20) (James Raspass)
    - Remove the executable bit from the test (GH#21) (James Raspass)
    - Add support for Windows four-digit year format (GH#23) (Grant Street
      Group)

(wen)