framemarket_grid_mp_list_products change grid to 3

we've changed the framemarket_grid_mp_list_products function to change the grid from 4 to 3. However I guess you've updated the framemarket theme in the last little while (I'm not directly involved in the site maintenance so not sure) as the grid has reverted back to 4.

Is there a way we can pull this function into a plugin or add it to our child theme's function file so the changes won't get blown away again?

also, if you could reply to that would be great.