Remove: すでに存在しない.yarn/plugins/のコピーをDockerfileたちから削除

[yonta]

fix #688

やったこと

• 存在しない.yarn/pluginsのCOPY節をDockerファイルから削除

[codecov[bot]]

Codecov Report

All modified and coverable lines are covered by tests :white_check_mark:

Comparison is base (e87fa6f) 96.55% compared to head (2c3225b) 96.55%. Report is 1 commits behind head on main.

Additional details and impacted files

```diff @@ Coverage Diff @@ ## main #689 +/- ## ======================================= Coverage 96.55% 96.55% ======================================= Files 17 17 Lines 319 319 ======================================= Hits 308 308 Misses 11 11 ```

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