fix(pytest[zshrc]): Fix `skipif` condition

[tony]

Would skip creation of .zshrc when not zsh (opposite of what's intended)

[codecov[bot]]

Codecov Report

Merging #292 (b02c192) into master (3a93f96) will not change coverage. The diff coverage is 0.00%.

:exclamation: Current head b02c192 differs from pull request most recent head 7631117. Consider uploading reports for the commit 7631117 to get more accurate results

@@           Coverage Diff           @@
##           master     #292   +/-   ##
=======================================
  Coverage   70.39%   70.39%           
=======================================
  Files          12       12           
  Lines        1064     1064           
  Branches      193      193           
=======================================
  Hits          749      749           
  Misses        287      287           
  Partials       28       28           

Impacted Files	Coverage Δ
src/unihan_etl/pytest_plugin.py	28.37% <0.00%> (ø)

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