Don't reset the render target when invalidating GPU renderer cache state

Fixes https://github.com/libsdl-org/SDL/issues/12646

(cherry picked from commit f35a2736b7)

src/render/gpu/SDL_render_gpu.c

@@ -445,7 +445,6 @@ static void GPU_InvalidateCachedState(SDL_Renderer *renderer)
 {
     GPU_RenderData *data = (GPU_RenderData *)renderer->internal;
 
-    data->state.render_target = NULL;
     data->state.scissor_enabled = false;
 }