Fixed doc block

src/ORM/Rule/ExistsIn.php

@@ -114,7 +114,7 @@ class ExistsIn
     }
 
     /**
-     * Check whether or not the entity fields nullable and null.
+     * Check whether or not the entity fields are nullable and null.
      *
      * @param \Cake\ORM\EntityInterface $entity The entity to check.
      * @param \Cake\ORM\Table $source The table to use schema from.