Fix test

Not sure why offset changed... probably different PCRE version calculates
them in different way.

Author: smalyshev

ext/pcre/tests/bug75457.phpt

@@ -6,5 +6,5 @@ $pattern = "/(((?(?C)0?=))(?!()0|.(?0)0)())/";
 var_dump(preg_match($pattern, "hello"));
 ?>
 --EXPECTF--
-Warning: preg_match(): Compilation failed: assertion expected after (?( or (?(?C) at offset 4 in %sbug75457.php on line %d
+Warning: preg_match(): Compilation failed: assertion expected after (?( or (?(?C) at offset 8 in %sbug75457.php on line %d
 bool(false)