Description:
------------
Wrong ReflectionType for sprintf/printf args parameter.

It should return ReflectionUnionType.

Test script:
---------------
<?php

foreach (['sprintf', 'printf'] as $functionName) {
	$rf = new ReflectionFunction($functionName);

	$rp = $rf->getParameters()[1];

	$rt = $rp->getType();

	var_dump($functionName);
	var_dump($rp->getName());
	var_dump($rt::class);
	if ($rt instanceof ReflectionNamedType) {
		var_dump($rt->getName());
	}
	var_dump('--------');
}



Expected result:
----------------
string(7) "sprintf"
string(4) "args"
string(19) "ReflectionUnionType"
string(8) "--------"
string(6) "printf"
string(4) "args"
string(19) "ReflectionUnionType"
string(8) "--------"

Actual result:
--------------
string(7) "sprintf"
string(4) "args"
string(19) "ReflectionNamedType"
string(39) "object|array|string|int|float|bool|null"
string(8) "--------"
string(6) "printf"
string(4) "args"
string(19) "ReflectionNamedType"
string(39) "object|array|string|int|float|bool|null"
string(8) "--------"