Fixed a anchor link for in the README
Fixed a anchor link for in the README

I changed a link called `#sort_order` to `#deterministic-ordering` as there was no `#sort_order` anchor in the README
froderik/closure_tree,mceachen/closure_tree,fabien-michel/closure_tree,seuros/closure_tree,procore/closure_tree,fabien-michel/closure_tree,mceachen/closure_tree,seuros/closure_tree,procore/closure_tree,seuros/closure_tree,froderik/closure_tree,fabien-michel/closure_tree,mceachen/closure_tree,froderik/closure_tree,procore/closure_tree