ci: explicitly install target rust version

[kanru]

No description provided.

[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 89.85%. Comparing base (33c4144) to head (fad1986).
Report is 3 commits behind head on master.

Additional details and impacted files

@@           Coverage Diff           @@
##           master     #675   +/-   ##
=======================================
  Coverage   89.85%   89.85%           
=======================================
  Files          42       42           
  Lines        8763     8763           
=======================================
  Hits         7874     7874           
  Misses        889      889           

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