docs: improve comment

Author: kenjis

system/Entity/Entity.php

@@ -553,7 +553,7 @@ protected function isMappedDbColumn(string $key): bool
     {
         $dbColumn = $this->mapProperty($key);
 
-        // Property name which has mapped column name
+        // The $key is a property name which has mapped db column name
         if ($key !== $dbColumn) {
             return false;
         }