[ticket/15174] Increase timeout for loading indicator

The timeout is rather low with 15 seconds until reporting
a timed out request. 25 seconds will be compatible with almost
any setup. A lot more changes would be needed to do proper
timeout checks on slow requests like purging the board cache.

PHPBB3-15174

phpBB/assets/javascript/core.js

@@ -41,7 +41,7 @@ phpbb.loadingIndicator = function() {
 			if ($loadingIndicator.is(':visible')) {
 				phpbb.alert($alert.attr('data-l-err'), $alert.attr('data-l-timeout-processing-req'));
 			}
-		}, 15000);
+		}, 25000);
 	}
 
 	return $loadingIndicator;