Also fix signature for passthru

Backported from a1a8d14
https://www.php.net/manual/en/function.passthru.php#refsect1-function.passthru-returnvalues

`passthru()` is false with invalid args
`passthru('command')` is null.

Author: TysonAndre

ext/opcache/Optimizer/zend_func_info.c

@@ -404,7 +404,7 @@ static const func_info_t func_infos[] = {
 	F1("system",                       MAY_BE_FALSE | MAY_BE_STRING),
 	F1("escapeshellcmd",               MAY_BE_NULL | MAY_BE_STRING),
 	F1("escapeshellarg",               MAY_BE_NULL | MAY_BE_STRING),
-	F1("passthru",                     MAY_BE_FALSE | MAY_BE_STRING),
+	F1("passthru",                     MAY_BE_NULL | MAY_BE_FALSE),
 	F1("shell_exec",                   MAY_BE_NULL | MAY_BE_FALSE | MAY_BE_STRING),
 #ifdef PHP_CAN_SUPPORT_PROC_OPEN
 	F1("proc_open",                    MAY_BE_FALSE | MAY_BE_RESOURCE),