Fix #11400: Increase default $g_view_configuration_threshold

By default, $g_view_configuration_threshold is currently set to
DEVELOPER. This option should really be changed to have a default of
ADMINISTRATOR, as the configuration of MantisBT can contain sensitive
information.

There won't be impact to current installations, as users at DEVELOPER
level have no links whatsoever in the UI to the adm_ and manage_ pages
of MantisBT.

config_defaults_inc.php

@@ -2700,7 +2700,7 @@
 	 * threshold for users to view the system configurations
 	 * @global int $g_view_configuration_threshold
 	 */
-	$g_view_configuration_threshold = DEVELOPER;
+	$g_view_configuration_threshold = ADMINISTRATOR;
 
 	/**
 	 * threshold for users to set the system configurations generically via MantisBT web interface.