Update version to 1.15.0-rc1

extra/simplesamlphp.spec

 %define name      simplesamlphp
 %define summary   SAML IDP/SP written in PHP
-%define version   dev
+%define version   1.15.0-rc1
 %define release   1
 %define license   LGPL 2.1
 %define group     Networking/WWW

lib/SimpleSAML/Configuration.php

@@ -386,7 +386,7 @@ class SimpleSAML_Configuration implements \SimpleSAML\Utils\ClearableState
      */
     public function getVersion()
     {
-        return 'master';
+        return '1.15.0-rc1';
     }