Add compat note to addSetEntry. [ci skip]

lodash.js

@@ -392,7 +392,7 @@
    * @returns {Object} Returns `map`.
    */
   function addMapEntry(map, pair) {
-    // Don't return `Map#set` because it doesn't return the map instance in IE 11.
+    // Don't return `map.set` because it's not chainable in IE 11.
     map.set(pair[0], pair[1]);
     return map;
   }
@@ -406,6 +406,7 @@
    * @returns {Object} Returns `set`.
    */
   function addSetEntry(set, value) {
+    // Don't return `set.add` because it's not chainable in IE 11.
     set.add(value);
     return set;
   }