lib/time: update vendored tzdata to release 2018e

It has been a long time since the last time the vendored zoneinfo in
lib/time was updated, and we're well into the freeze. Update it to the
lastest release from IANA.

Updates #22487

Change-Id: Ib9a8eb409554848285fc88363dbb04ed9d6d9eb0
Reviewed-on: https://go-review.googlesource.com/117855Reviewed-by: Brad Fitzpatrick <bradfitz@golang.org>

lib/time/update.bash

@@ -8,8 +8,8 @@
 # Consult https://www.iana.org/time-zones for the latest versions.
 
 # Versions to use.
-CODE=2017c
-DATA=2017c
+CODE=2018e
+DATA=2018e
 
 set -e
 rm -rf work