Use internal texture at internal resolution for calculating luminance.

Fixes an error where the exposure was calculated incorrectly if a lower resolution scale was used while using FSR2. Now the behavior is consistent regardless of the resolution scale.

servers/rendering/renderer_rd/renderer_scene_render_rd.cpp

@@ -418,7 +418,7 @@ void RendererSceneRenderRD::_render_buffers_post_process_and_tonemap(const Rende
 		double step = RSG::camera_attributes->camera_attributes_get_auto_exposure_adjust_speed(p_render_data->camera_attributes) * time_step;
 		float auto_exposure_min_sensitivity = RSG::camera_attributes->camera_attributes_get_auto_exposure_min_sensitivity(p_render_data->camera_attributes);
 		float auto_exposure_max_sensitivity = RSG::camera_attributes->camera_attributes_get_auto_exposure_max_sensitivity(p_render_data->camera_attributes);
-		luminance->luminance_reduction(color_texture, color_size, luminance_buffers, auto_exposure_min_sensitivity, auto_exposure_max_sensitivity, step, set_immediate);
+		luminance->luminance_reduction(rb->get_internal_texture(), rb->get_internal_size(), luminance_buffers, auto_exposure_min_sensitivity, auto_exposure_max_sensitivity, step, set_immediate);
 
 		// Swap final reduce with prev luminance.