app: use the default scenegraph render backend(OpenGL) on Windows

We've had reports of missing vulkan dependencies on fresh Windows
10 installs. Until this has been investigated, we should keep the
default rendering backend at the cost of some flicker.

Change-Id: Idaab06ff80d7841231270a207cceb134f8d790b0

src/main.cpp

@@ -91,8 +91,6 @@ main(int argc, char* argv[])
 
 #if defined(Q_OS_MACOS)
     QQuickWindow::setGraphicsApi(QSGRendererInterface::MetalRhi);
-#elif defined(Q_OS_WIN)
-    QQuickWindow::setGraphicsApi(QSGRendererInterface::VulkanRhi);
 #endif
 
     auto newArgv = parseInputArgument(argc, argv, qtWebEngineChromiumFlags);