Prepare the 2.15.4 release

CHANGELOG

@@ -1,4 +1,4 @@
-# 2.15.4 (2022-XX-XX)
+# 2.15.4 (2022-12-27)
 
  * Fix optimizing closures callbacks
  * Add a better exception when getting an undefined constant via `constant`

src/Environment.php

@@ -38,12 +38,12 @@ use Twig\TokenParser\TokenParserInterface;
  */
 class Environment
 {
-    public const VERSION = '2.15.4-DEV';
+    public const VERSION = '2.15.4';
     public const VERSION_ID = 21504;
     public const MAJOR_VERSION = 2;
     public const MINOR_VERSION = 15;
     public const RELEASE_VERSION = 4;
-    public const EXTRA_VERSION = 'DEV';
+    public const EXTRA_VERSION = '';
 
     private $charset;
     private $loader;