Remove TODO

RyanCavanaugh · RyanCavanaugh · commit 100262537a68 · 2017-12-13T10:58:04.000-08:00
diff --git a/src/lib/es5.d.ts b/src/lib/es5.d.ts
@@ -992,7 +992,6 @@ interface ReadonlyArray<T> {
       * Combines two or more arrays.
       * @param items Additional items to add to the end of array1.
       */
-    // TODO: https://github.com/Microsoft/TypeScript/issues/20454
     concat(...items: (T[] | ReadonlyArray<T>)[]): T[];
     /**
       * Combines two or more arrays.
