Update output-theming.md

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[skip ci] Update output-data-widgets.md

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[skip ci] Update output-formatter.md

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Docs guide ja intro revised　[ci skip]

Docs guide ja start revised [ci skip]

docs/guide-ja/intro-upgrade-from-v1.md - revised using "初期設定" and "設定情報" for "configuration(s)" [ci skip]

Fixes #5480: Added defensive code to `yii\web\User::getIdentity()` to avoid potential infinite recursion

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[skip ci] Update input-file-upload.md

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[skip ci] Update input-validation.md

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[skip ci] Update input-forms.md

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