Update IANA to tz 2020d
https://bugs.chromium.org/p/chromium/issues/detail?id=1143059

Briefly:
     Palestine ends DST earlier than predicted, on 2020-10-24.

   Changes to past and future timestamps

     Palestine ends DST on 2020-10-24 at 01:00, instead of 2020-10-31
     as previously predicted (thanks to Sharef Mustafa.)  Its
     2019-10-26 fall-back was at 00:00, not 01:00 (thanks to Steffen
     Thorsen.)  Its 2015-10-23 transition was at 01:00 not 00:00, and
     its spring 2020 transition was on March 28 at 00:00, not March 27
     (thanks to Pierre Cashon.)  This affects Asia/Gaza and
     Asia/Hebron.  Assume future spring and fall transitions will be on
     the Saturday preceding the last Sunday of March and October,
     respectively.

TBR=jshin@chromium.org
Bug: 1143059
Change-Id: Ida3e468cb70575c68dd121da0836ecf523828c8b
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/deps/icu/+/2504367
Reviewed-by: Frank Tang <ftang@chromium.org>
Reviewed-on: https://fuchsia-review.googlesource.com/c/third_party/icu/+/449855
Reviewed-by: Fabrice de Gans-Riberi <fdegans@google.com>
9 files changed