tools: update tzdata to 2021a4

This updates the time zone database up to 2021a4 for the node
v12.x-staging branch, following the documentation at
https://github.com/nodejs/node/blob/master/doc/guides/maintaining-icu.md#time-zone-data

This is essentially a backport of #40658.

Refs: #40658
Refs: nodejs/Release#576

Author: albertyw