MAGETWO-85930: Backport PR8418 - Fatal error on cms block grid delete #12840

 - Merge Pull Request #12840 from duckchip/magento2:Backport-#8418
 - Merged commits:
   1. 8059598

Author: miguelbalparda

app/code/Magento/Cms/Model/ResourceModel/Block/Grid/Collection.php

@@ -84,19 +84,6 @@ public function setAggregations($aggregations)
         $this->aggregations = $aggregations;
     }
 
-    /**
-     * Retrieve all ids for collection
-     * Backward compatibility with EAV collection
-     *
-     * @param int $limit
-     * @param int $offset
-     * @return array
-     */
-    public function getAllIds($limit = null, $offset = null)
-    {
-        return $this->getConnection()->fetchCol($this->_getAllIdsSelect($limit, $offset), $this->_bindParams);
-    }
-
     /**
      * Get search criteria.
      *