Changes the class member we modify to uniques

The class member property we modify in Faker’s UniqueGenerator is
uniques, that UniqueGenerator’s class methods then access to check for
unique data.

api/tests/Traits/HelpersTrait.php

@@ -41,7 +41,7 @@ protected function getFakerWithUniqueUserData()
         $unique = $faker->unique();
 
         $binder = function ($value) {
-            $this->uniqueUserValues = $value;
+            $this->uniques = $value;
         };
 
         $uniqueBinder = $binder->bindTo($unique, $unique);