[Spice_announce] No new leap second at the end of December 2022

[Boris Semenov]

The IERS announced there will NOT be a new leap second declared at 
midnight on December 31, 2022:

    https://datacenter.iers.org/data/latestVersion/16_BULLETIN_C16.txt

As a consequence, the current SPICE LSK, naif0012.tls, will remain 
current until at least July 01, 2023.