Fix #106568: Overlay: Resolve motion path rendering in Metal

Resolve small indexing issue in Metal implementation
of motion path line rendering.

Authored by Apple: Michael Parkin-White

Pull Request: blender/blender#106595

source/blender/draw/engines/overlay/shaders/overlay_motion_path_line_vert_no_geom.glsl

@@ -118,7 +118,7 @@ void main()
   vec4 finalColor_geom[2];
 
   do_vertex_shader(out_pos0, base_vertex_id, ssPos[0], finalColor_geom[0]);
-  do_vertex_shader(out_pos1, base_vertex_id + 1, ssPos[0], finalColor_geom[0]);
+  do_vertex_shader(out_pos1, base_vertex_id + 1, ssPos[1], finalColor_geom[1]);
 
   /* Geometry shader alternative -- Output is trianglelist consisting of 6 vertices.
    * Each vertex shader invocation is one vertex in the output primitive, so outptut