Fixes draw_rectangle_color

Because of the vertice order it was producing different gradients than GM8.1 when testing the following code.
```
d3d_set_culling(true);
draw_rectangle_color(0,0,50,50,c_red,c_green,c_blue,c_purple,false);
```
The order of the vertices I have changed it to appears to work fine with culling.