Removed DB2SchemaManager::_getPortableForeignKeyRuleDef()

UPGRADE.md

 # Upgrade to 3.0
 
+## BC BREAK `DB2SchemaManager::_getPortableForeignKeyRuleDef()` removed
+
+The method was used internally and is no longer needed.
+
 ## BC BREAK `AbstractPlatform::get*Expression()` methods no loner accept integer values as arguments
 
 The following methods' arguments do not longer accept integer value:

lib/Doctrine/DBAL/Schema/DB2SchemaManager.php

@@ -181,22 +181,6 @@ class DB2SchemaManager extends AbstractSchemaManager
         return parent::_getPortableTableForeignKeysList($foreignKeys);
     }
 
-    /**
-     * {@inheritdoc}
-     */
-    protected function _getPortableForeignKeyRuleDef($def)
-    {
-        if ($def === 'C') {
-            return 'CASCADE';
-        }
-
-        if ($def === 'N') {
-            return 'SET NULL';
-        }
-
-        return null;
-    }
-
     /**
      * {@inheritdoc}
      */