[v12.x] 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 partial backport of https://github.com/nodejs/node/pull/40658.
Refs: https://github.com/nodejs/node/pull/40658 Refs: https://github.com/nodejs/Release/issues/576