bootmanager: Use QStringLiteral instead of std::string to represent the window title

This gets rid of an unnecessary type conversion. We can just use the
regular QStringLiteral to already format the string as the type
setWindowTitle accepts instead of converting from a std::string
instance.

src/citra_qt/bootmanager.cpp

@@ -109,9 +109,8 @@ private:
 GRenderWindow::GRenderWindow(QWidget* parent, EmuThread* emu_thread)
     : QWidget(parent), child(nullptr), emu_thread(emu_thread) {
 
-    std::string window_title = fmt::format("Citra {} | {}-{}", Common::g_build_name,
-                                           Common::g_scm_branch, Common::g_scm_desc);
-    setWindowTitle(QString::fromStdString(window_title));
+    setWindowTitle(QStringLiteral("Citra %1 | %2-%3")
+                       .arg(Common::g_build_name, Common::g_scm_branch, Common::g_scm_desc));
     setAttribute(Qt::WA_AcceptTouchEvents);
 
     InputCommon::Init();