finish off tests.tseries.test_timezones

[jbrockmendel]

• closes #xxxx
• tests added / passed
• passes git diff upstream/master -u -- "*.py" | flake8 --diff
• whatsnew entry

[codecov]

Codecov Report

Merging #19739 into master will not change coverage.
The diff coverage is n/a.

@@           Coverage Diff           @@
##           master   #19739   +/-   ##
=======================================
  Coverage   91.58%   91.58%           
=======================================
  Files         150      150           
  Lines       48862    48862           
=======================================
  Hits        44750    44750           
  Misses       4112     4112

Flag	Coverage Δ
#multiple	89.95% <ø> (ø)	⬆️
#single	41.75% <ø> (ø)	⬆️

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[jreback]

thanks!