AC-9831: Block template render enhancement

	 * code change as per review comment

Author: rizwankhgl

app/code/Magento/Email/Model/Template/Filter.php

@@ -81,11 +81,6 @@ class Filter extends Template
      */
     protected $_modifiers = ['nl2br' => ''];
 
-    /**
-     * @var string
-     */
-    private const CACHE_KEY_PREFIX = "EMAIL_FILTER_";
-
     /**
      * @var bool
      */