rm useless comment

Author: etpinard

src/plots/plots.js

@@ -762,9 +762,6 @@ plots.purge = function(gd) {
     // note: we DO NOT remove _context because it doesn't change when we insert
     // a new plot, and may have been set outside of our scope.
 
-    // clean up the gl and geo containers
-    // TODO unify subplot creation/update with d3.selection.order
-    // and/or subplot ids
     var fullLayout = gd._fullLayout || {};
     if(fullLayout._glcontainer !== undefined) fullLayout._glcontainer.remove();
     if(fullLayout._geocontainer !== undefined) fullLayout._geocontainer.remove();