fix missing ibl reconstruction from dfg multiscattering

servers/rendering/renderer_rd/shaders/forward_clustered/scene_forward_clustered.glsl

@@ -2078,7 +2078,7 @@ void fragment_shader(in SceneData scene_data) {
 
 		// cheap luminance approximation
 		float f90 = clamp(50.0 * f0.g, metallic, 1.0);
-		indirect_specular_light *= energy_compensation * (f90 * envBRDF.x + f0 * envBRDF.y);
+		indirect_specular_light *= energy_compensation * ((f90 - f0) * envBRDF.x + f0 * envBRDF.y);
 #endif
 	}