RegTest: Fix flipped images in OpenGL

We're reading the framebuffer, not rendered image.

src/duckstation-regtest/regtest_host.cpp

@@ -457,13 +457,9 @@ void Host::FrameDoneOnGPUThread(GPUBackend* gpu_backend, u32 frame_number)
     return;
   }
 
-  System::QueueAsyncTask([path = std::move(path), fp = fp.release(), flip_y = g_gpu_device->UsesLowerLeftOrigin(),
-                          image = std::move(image)]() mutable {
+  System::QueueAsyncTask([path = std::move(path), fp = fp.release(), image = std::move(image)]() mutable {
     Error error;
 
-    if (flip_y)
-      image.FlipY();
-
     if (image.GetFormat() != ImageFormat::RGBA8)
     {
       std::optional<Image> convert_image = image.ConvertToRGBA8(&error);