[9.x] Apply same syntax of startsWith on endsWith

[cesarkohl]

Hey guys, this is my first time ever contributing to an oss project. I've been looking for the first project and recently have chosen Laravel :)

There are two related functions, startsWith() and endsWith(), with quite similar behavior. Despite that, the syntax on the conditional is a bit different.

This PR improves the endsWith() using the same syntax on the startsWith() conditional.

// Illuminate/Support/Str.php:902
if ((string) $needle !== '' && str_starts_with($haystack, $needle)) {