update iterator join links

Author: zloirock

docs/web/docs/features/proposals/iterator-join.md

@@ -1,6 +1,6 @@
 # Iterator join
-[Specification](https://bakkot.github.io/proposal-iterator-join/)\
-[Proposal repo](https://github.com/bakkot/proposal-iterator-join)
+[Specification](https://tc39.es/proposal-iterator-join)\
+[Proposal repo](https://github.com/tc39/proposal-iterator-join)
 
 ## Modules
 [`esnext.iterator.join`](https://github.com/zloirock/core-js/blob/v4/packages/core-js/modules/esnext.iterator.join.js)

packages/core-js/modules/esnext.iterator.join.js

@@ -13,7 +13,7 @@ var $join = uncurryThis([].join);
 var push = uncurryThis([].push);
 
 // `Iterator.prototype.join` method
-// https://bakkot.github.io/proposal-iterator-join/
+// https://github.com/tc39/proposal-iterator-join
 // @dependency: es.iterator.constructor
 $({ target: 'Iterator', proto: true, real: true, forced: true }, {
   join: function join(separator) {