yuzu/bootmanager: Resolve constructor initializer list warnings

Resolves -Wreorder warnings. These will automatically be initialized to
nullptr anyways, so these were redundant.

src/yuzu/bootmanager.cpp

@@ -186,8 +186,7 @@ private:
 };
 
 GRenderWindow::GRenderWindow(QWidget* parent, EmuThread* emu_thread)
-    : QWidget(parent), child(nullptr), context(nullptr), emu_thread(emu_thread) {
-
+    : QWidget(parent), emu_thread(emu_thread) {
     setWindowTitle(QStringLiteral("yuzu %1 | %2-%3")
                        .arg(Common::g_build_name, Common::g_scm_branch, Common::g_scm_desc));
     setAttribute(Qt::WA_AcceptTouchEvents);