Add Japanese translation for "warning"

Author: tats-u

packages/docusaurus-theme-translations/locales/ja/theme-common.json

@@ -19,7 +19,7 @@
   "theme.admonition.info": "備考",
   "theme.admonition.note": "注記",
   "theme.admonition.tip": "ヒント",
-  "theme.admonition.warning": "warning",
+  "theme.admonition.warning": "警告",
   "theme.blog.archive.description": "アーカイブ",
   "theme.blog.archive.title": "アーカイブ",
   "theme.blog.paginator.navAriaLabel": "ブログ記事一覧のナビゲーション",