Revert changes to isSubsetOf

Author: koddsson

lib/chai/core/assertions.js

@@ -3043,9 +3043,7 @@ Assertion.addMethod('closeTo', closeTo);
 Assertion.addMethod('approximately', closeTo);
 
 // Note: Duplicates are ignored if testing for inclusion instead of sameness.
-function isSubsetOf(_subset, _superset, cmp, contains, ordered) {
-  let superset = Array.from(_superset);
-  let subset = Array.from(_subset);
+function isSubsetOf(subset, superset, cmp, contains, ordered) {
   if (!contains) {
     if (subset.length !== superset.length) return false;
     superset = superset.slice();