Fix #227: finalize ConfigException

Author: rustamwin

src/Exception/ConfigException.php

@@ -6,11 +6,7 @@
 
 use Exception;
 
-/**
- * @final Will be marked as final in next major version
- * @todo Remove this note and make the class final
- */
-class ConfigException extends Exception
+final class ConfigException extends Exception
 {
     /**
      * @param string[] $section Config path