php8: avoid named parameters in call_user_func_array

[joebordes]

I just ran into this issue in another project while evaluating PHP 8 support.

https://php.watch/versions/8.0/named-parameters#named-params-call_user_func_array

PHP 8 supports named parameters and call_user_func_array uses that when the parameter array has keys.

I don't know if the "array_values" solution is needed in Valitron or not but I thought I would share just in case.