fix: remove maybe_unused attribute and add Q_UNUSED

[18202781743]

Removed the [[maybe_unused]] attribute from the QtConcurrent::run result
variable and replaced it with Q_UNUSED macro. This change was made
because:

1. [[maybe_unused]] is a C++17 feature that might not be supported in
   all build environments
2. Q_UNUSED is the Qt-specific and more portable way to suppress unused
   variable warnings
3. Maintains consistency with Qt coding standards
4. The variable is intentionally unused as we're running the task
   asynchronously without tracking the result

fix: 移除 maybe_unused 属性并添加 Q_UNUSED

移除了 QtConcurrent::run 结果变量的 [[maybe_unused]] 属性，改用 Q_UNUSED
宏。此变更的原因是：

1. [[maybe_unused]] 是 C++17 特性，可能在某些构建环境中不受支持
2. Q_UNUSED 是 Qt 特有的更便携的方式来抑制未使用变量警告
3. 保持与 Qt 编码标准的一致性
4. 该变量是故意不使用的，因为我们异步运行任务而不跟踪结果

[deepin-ci-robot]

deepin pr auto review

关键摘要:

• 在QtConcurrent::run调用中，result变量被声明为auto类型，但在函数末尾被Q_UNUSED(result)忽略，这可能是为了防止编译器警告，但应该确认是否有必要。
• QSaveFile的setDirectWriteFallback(true)调用增加了缓存文件能被成功保存的概率，这是一个好的做法。

是否建议立即修改:

• 是，应该确认result变量的使用是否必要，如果不需要，应该移除相关代码以避免混淆。

[deepin-ci-robot]

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This pull-request has been approved by: 18202781743, mhduiy

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