defaultnormal_vertex: terser code

src/renderers/shaders/ShaderChunk/defaultnormal_vertex.glsl

@@ -1,10 +1,8 @@
-#ifdef FLIP_SIDED
-
-	vec3 transformedNormal = - normalMatrix * objectNormal;
+vec3 transformedNormal = normalMatrix * objectNormal;
 
-#else
+#ifdef FLIP_SIDED
 
-	vec3 transformedNormal = normalMatrix * objectNormal;
+	transformedNormal = - transformedNormal;
 
 #endif