Issue #3453068 by kalpanajaiswal, BenStallings: Sort::fields property is...

Issue #3453068 by kalpanajaiswal, BenStallings: Sort::fields property is incorrectly defined as a string

(cherry picked from commit 9f6143c1)

core/modules/jsonapi/src/Query/Sort.php

@@ -47,7 +47,7 @@ class Sort {
   /**
    * The fields on which to sort.
    *
-   * @var string
+   * @var array
    */
   protected $fields;