lib/time: update tz data to 2019c

Updates #22487

Change-Id: I32dcd604af84e2000196d64bf69c67f81535290a
Reviewed-on: https://go-review.googlesource.com/c/go/+/208797
Run-TryBot: Tobias Klauser <tobias.klauser@gmail.com>
TryBot-Result: Gobot Gobot <gobot@golang.org>
Reviewed-by: Tobias Klauser <tobias.klauser@gmail.com>

lib/time/update.bash

@@ -8,8 +8,8 @@
 # Consult https://www.iana.org/time-zones for the latest versions.
 
 # Versions to use.
-CODE=2019b
-DATA=2019b
+CODE=2019c
+DATA=2019c
 
 set -e
 rm -rf work