Fixed the DateTime constraint deprecation

Author: javiereguiluz

src/Entity/Comment.php

@@ -64,7 +64,6 @@ class Comment
      * @var \DateTime
      *
      * @ORM\Column(type="datetime")
-     * @Assert\DateTime
      */
     private $publishedAt;
 

src/Entity/Post.php

@@ -87,7 +87,6 @@ class Post
      * @var \DateTime
      *
      * @ORM\Column(type="datetime")
-     * @Assert\DateTime
      */
     private $publishedAt;