Fix for GLES3 radiance cubemap update

(cherry picked from commit 3038de42452f0bb840722d2dfc84ca996f0c126b)

drivers/gles3/rasterizer_scene_gles3.cpp

@@ -933,7 +933,7 @@ void RasterizerSceneGLES3::_update_sky_radiance(RID p_env, const Projection &p_p
 	int max_processing_layer = sky->mipmap_count;
 
 	// Update radiance cubemap
-	if (sky->reflection_dirty && (sky->processing_layer > max_processing_layer || update_single_frame)) {
+	if (sky->reflection_dirty && (sky->processing_layer >= max_processing_layer || update_single_frame)) {
 		static const Vector3 view_normals[6] = {
 			Vector3(+1, 0, 0),
 			Vector3(-1, 0, 0),