Bump to FreshRSS 1.15.3

constants.php

@@ -2,7 +2,7 @@
 //NB: Do not edit; use ./constants.local.php instead.
 
 //<Not customisable>
-define('FRESHRSS_VERSION', '1.15.3-dev');
+define('FRESHRSS_VERSION', '1.15.3');
 define('FRESHRSS_WEBSITE', 'https://freshrss.org');
 define('FRESHRSS_WIKI', 'https://freshrss.github.io/FreshRSS/');