Default to using 2020d tzdata

[omus]

Release notes:

• 2020b: http://mm.icann.org/pipermail/tz-announce/2020-October/000059.html
• 2020c: http://mm.icann.org/pipermail/tz-announce/2020-October/000060.html
• 2020d: http://mm.icann.org/pipermail/tz-announce/2020-October/000062.html

[codecov-io]

Codecov Report

Merging #304 into master will increase coverage by 0.13%.
The diff coverage is 100.00%.

@@            Coverage Diff             @@
##           master     #304      +/-   ##
==========================================
+ Coverage   93.72%   93.86%   +0.13%     
==========================================
  Files          32       32              
  Lines        1530     1532       +2     
==========================================
+ Hits         1434     1438       +4     
+ Misses         96       94       -2     

Impacted Files	Coverage Δ
src/tzdata/version.jl	91.42% <ø> (ø)
src/tzdata/build.jl	68.18% <100.00%> (+6.27%)	⬆️

---

Continue to review full report at Codecov.

Legend - Click here to learn more
Δ = absolute <relative> (impact), ø = not affected, ? = missing data
Powered by Codecov. Last update f07796f...ee191e9. Read the comment docs.