Fix Zsh completion install

[tiangolo]

🐛 Fix Zsh completion install

[github-actions]

🚀 Deployed on https://5e72831bd832c00179f56363--typertiangolo.netlify.com

[codecov-io]

Codecov Report

Merging #69 into master will not change coverage by %.
The diff coverage is 100.00%.

@@           Coverage Diff           @@
##           master      #69   +/-   ##
=======================================
  Coverage   99.92%   99.92%           
=======================================
  Files         210      210           
  Lines        3933     3933           
=======================================
  Hits         3930     3930           
  Misses          3        3           

Impacted Files	Coverage Δ
.../test_completion/test_completion_install_source.py	100.00% <ø> (ø)
tests/test_completion/test_completion_install.py	97.36% <100.00%> (ø)
typer/completion.py	100.00% <100.00%> (ø)

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