Fix iterate these (again)

src/lib/Iterate.vala

@@ -24,17 +24,17 @@ namespace Invercargill.Iterate {
     }
 
     public static Enumerable<T> these<T>(owned T item1, ...) {
-        var series = new Series<T>();
+        var vector = new Vector<T>();
         var args = va_list();
-        series.add(item1);
+        vector.add(item1);
         while(true) {
             T? item = args.arg<T>();
             if(item == null) {
                 break;
             }
-            series.add((owned)item);
+            vector.add((owned)item);
         }
-        return series.to_buffer().seal();
+        return vector.to_buffer().seal();
     }
 
     public static Enumerable<T> deferred<T>(owned Generators.DeferredDelegate<T> function) {