fix(i18n): translate the Scrollback label into Chinese

It was the only English row label in a Chinese Scrolling section, sitting
between 滚动速度 and 平滑滚动 with its own description already in Chinese
— Japanese had translated it, Chinese had not. zh keeps English for the
tokens you type (shell, PATH, SSH); a row label is not one of those.

src/ui/i18n/mod.rs

@@ -1297,7 +1297,6 @@ mod tests {
             L10nKey::SettingsProxyCommand,
             L10nKey::SftpContextChmod,
             L10nKey::SettingsShell,
-            L10nKey::SettingsScrollback,
             L10nKey::SettingsScrollbackDesc,
             L10nKey::SettingsScrollSpeed,
             L10nKey::SettingsScrollSpeedDesc,

src/ui/i18n/zh.rs

@@ -276,7 +276,7 @@ pub fn translate_zh(key: L10nKey) -> Option<&'static str> {
             "仅适用于没有可继承目录的 shell，例如窗口的第一个标签页。新标签页和分屏仍会继承活动窗格的目录，已经打开的 shell 会继续运行。"
         }
         L10nKey::SettingsScrolling => "滚动",
-        L10nKey::SettingsScrollback => "Scrollback",
+        L10nKey::SettingsScrollback => "回滚行数",
         L10nKey::SettingsScrollbackDesc => "每个窗格保留的历史行数。仅适用于新窗格。",
         L10nKey::SettingsScrollSpeed => "滚动速度",
         L10nKey::SettingsScrollSpeedDesc => "应用于鼠标滚轮滚动的倍率。",