Update bug-13481-before-php83.php

Author: staabm

tests/PHPStan/Analyser/nsrt/bug-13481-before-php83.php

@@ -6,15 +6,15 @@
 
 function bug13481() {
 	$s = 'ab c1';
-	assertType("'ab c2'", str_increment($s));
+	assertType("*ERROR*", str_increment($s));
 
 	++$s;
 	assertType("'ab c2'", $s);
 }
 
 function bug13481b() {
 	$s = '%';
-	assertType("'%'", str_increment($s));
+	assertType("*ERROR*", str_increment($s));
 
 	++$s;
 	assertType("'%'", $s);