ENGCOM-2358: [Backport] Fixed type hints and docs for Downloadable Samples block #16825

 - Merge Pull Request #16825 from ronak2ram/magento2:2.1-develop-PR-port-16408
 - Merged commits:
   1. 6698036
   2. 82150c6

Author: magento-engcom-team

app/code/Magento/Downloadable/Block/Catalog/Product/Samples.php

@@ -8,7 +8,8 @@
 
 namespace Magento\Downloadable\Block\Catalog\Product;
 
-use Magento\Downloadable\Model\ResourceModel\Sample;
+use Magento\Downloadable\Model\ResourceModel\Sample\Collection as SampleCollection;
+use Magento\Downloadable\Api\Data\SampleInterface;
 
 /**
  * Downloadable Product Samples part block
@@ -30,15 +31,15 @@ public function hasSamples()
     /**
      * Get downloadable product samples
      *
-     * @return array
+     * @return SampleCollection
      */
     public function getSamples()
     {
         return $this->getProduct()->getTypeInstance()->getSamples($this->getProduct());
     }
 
     /**
-     * @param Sample $sample
+     * @param SampleInterface $sample
      * @return string
      */
     public function getSampleUrl($sample)