Revert "assert a invalid constant turns into mixed"

This reverts commit 42307ce.

e2e/bug10483/bootstrap.php

@@ -3,4 +3,3 @@
 // constant that's used in the Filter extension that was introduced in a later version of PHP.
 // on earlier php version introduce the same constant via a bootstrap file but with a wrong type
 if(!defined("FILTER_SANITIZE_ADD_SLASHES"))define("FILTER_SANITIZE_ADD_SLASHES",false);
-if(!defined("FILTER_SANITIZE_MAGIC_QUOTES"))define("FILTER_SANITIZE_MAGIC_QUOTES",false);

e2e/bug10483/src/bug10483.php

@@ -1,11 +1,5 @@
 <?php
 
-use function PHPStan\Testing\assertType;
-
 function doFoo(mixed $filter): void {
-	assertType('non-falsy-string|false', filter_var("no", FILTER_VALIDATE_REGEXP));
-
-	// if FILTER_SANITIZE_MAGIC_QUOTES would contain a valid value, the following line would yield "string|false".
-	// but since in phpstan bootstrap file the constant was miss-defined with a invalid value, PHPStan does not know the constant and returns "mixed", like for regular unknown constants.
-	assertType('mixed', filter_var($filter, FILTER_SANITIZE_MAGIC_QUOTES));
+    \PHPStan\Testing\assertType('non-falsy-string|false', filter_var("no", FILTER_VALIDATE_REGEXP));
 }