yuzu/wait_tree: Pass QString by value and std::move in the initializer list for WaitTreeText

Just a trivial modernization that potentially avoids copying strings in certain scenarios.

src/yuzu/debugger/wait_tree.cpp

@@ -75,7 +75,7 @@ std::vector<std::unique_ptr<WaitTreeThread>> WaitTreeItem::MakeThreadItemList()
     return item_list;
 }
 
-WaitTreeText::WaitTreeText(const QString& t) : text(t) {}
+WaitTreeText::WaitTreeText(QString t) : text(std::move(t)) {}
 WaitTreeText::~WaitTreeText() = default;
 
 QString WaitTreeText::GetText() const {