ENGCOM-1936: [Forwardport] Wrong annotation in _toOptionArray : lib\internal\Magento\Framework\D… #15944

 - Merge Pull Request #15944 from vgelani/magento2:2.3-develop-PR-port-15892
 - Merged commits:
   1. 681e65f
   2. cb0108f

Author: magento-engcom-team

lib/internal/Magento/Framework/Data/SearchResultProcessor.php

@@ -188,8 +188,8 @@ public function toArray($arrRequiredFields = [])
     }
 
     /**
-     * @param null $valueField
-     * @param null $labelField
+     * @param string|null $valueField
+     * @param string|null $labelField
      * @param array $additional
      * @return array
      */