No leap second on 2019-12-31.

Per IERS Bulletin C 58 (2019-07-04), no leap second on 2019-12-31.
https://hpiers.obspm.fr/iers/bul/bulc/bulletinc.58

* leap-seconds.list: Update file from NIST, retrieved from
<ftp://ftp.nist.gov/pub/time/leap-seconds.list>.

leap-seconds.list

@@ -204,10 +204,10 @@
 #	current -- the update time stamp, the data and the name of the file
 #	will not change.
 #
-#	Updated through IERS Bulletin C57
-#	File expires on:  28 December 2019
+#	Updated through IERS Bulletin C58
+#	File expires on:  28 June 2020
 #
-#@	3786480000
+#@	3802291200 
 #
 2272060800	10	# 1 Jan 1972
 2287785600	11	# 1 Jul 1972
@@ -252,4 +252,4 @@
 #	the hash line is also ignored in the
 #	computation.
 #
-#h 	83c68138 d3650221 07dbbbcd 11fcc859 ced1106a
+#h 	f28827d2 f263b6c3 ec0f19eb a3e0dbf0 97f3fa30