removed return type from Container::__call() [Closes nette/utils#338]

The fatal error appears only when a subclass extends Form/Container AND
re-applies the SmartObject trait, e.g.:

Author: dg

src/Forms/Container.php

@@ -604,8 +604,11 @@ public function addContainer(string|int $name): self
 	/********************* extension methods ****************d*g**/
 
 
-	/** @param mixed[] $args */
-	public function __call(string $name, array $args): mixed
+	/**
+	 * @param  mixed[]  $args
+	 * @return mixed
+	 */
+	public function __call(string $name, array $args)
 	{
 		if (isset(self::$extMethods[$name])) {
 			return (self::$extMethods[$name])($this, ...$args);