Replace stubs/Stringable.php with symfony/polyfill-php80

[reedy]

Any chance we could replace stubs/Stringable.php with symfony/polyfill-php80?

For those of running on PHP 8.0+, it's much easier to replace-away a composer library that we know we don't need...

[marc-mabe]

Why do you need to "replace-away" it? It's not loaded if you are running on PHP 8.0+ anyway.

[marc-mabe]

closing as unclear