Prepare the 3.15.0 release

Author: fabpot

src/Environment.php

@@ -44,12 +44,12 @@
  */
 class Environment
 {
-    public const VERSION = '3.15.0-DEV';
+    public const VERSION = '3.15.0';
     public const VERSION_ID = 31500;
     public const MAJOR_VERSION = 3;
     public const MINOR_VERSION = 15;
     public const RELEASE_VERSION = 0;
-    public const EXTRA_VERSION = 'DEV';
+    public const EXTRA_VERSION = '';
 
     private $charset;
     private $loader;