fix(settings): remove ineffective max reasoning effort level for Claude Code

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

src/i18n/messages/ja.json

@@ -631,8 +631,7 @@
       "effortLevelDefault": "デフォルトレベル",
       "effortLevel_low": "低",
       "effortLevel_medium": "中",
-      "effortLevel_high": "高",
-      "effortLevelMax": "最大（Opus のみ対応）"
+      "effortLevel_high": "高"
     },
     "dialogs": {
       "confirmDeleteProvider": "Provider {providerId} を削除しますか？",