i18n(metadata): translate the fetch summary 'Drive Offline' stat

Reuses each locale's established rootOffline rendering from the scoped
scan feature (§2 'Scoped scan and root availability').

locales/ja.json

@@ -2130,7 +2130,7 @@
             "statSuccess": "成功",
             "statFailed": "失敗",
             "statSkipped": "スキップ",
-            "statOffline": "[TODO: Translate] Drive Offline",
+            "statOffline": "ドライブ オフライン",
             "statTotal": "スキャン合計",
             "statDuration": "所要時間",
             "successMessage": "すべての{count}件の{type}を正常に更新しました",