Simplify code

src/renderers/shaders/ShaderLib/background_vert.glsl

@@ -5,7 +5,6 @@ void main() {
 
 	vUv = ( uvTransform * vec3( uv, 1 ) ).xy;
 
-	gl_Position = vec4( position, 1.0 );
-	gl_Position.z = 1.0;
+	gl_Position = vec4( position.xy, 1.0, 1.0 );
 
 }