Stop importing the php82 polyfill in DefaultSchemaFilesProviderTest

[Steveb-p]

🎫 Issue	IBX-XXXXX

Description:

PHPStan dies on PHP 7.4 before reporting anything, so every PR against 4.6 fails the
Tests (7.4) job regardless of what it changes — currently #42, #43 and #44, one of which is an
eleven-line change to a single method:

Child process error (exit code 255): PHP Fatal error: Cannot redeclare
Ibexa\PolyfillPhp82\iterator_to_array() (previously declared in
vendor/ibexa/polyfill-php82/src/iterator_to_array.php:18) ... while running parallel worker

ibexa/polyfill-php82 v1.0.1 lists src/iterator_to_array.php in both autoload.files and
autoload.psr-4 (Ibexa\PolyfillPhp82\ → src/), and the function has no function_exists()
guard. Analysing the use function Ibexa\PolyfillPhp82\iterator_to_array; in
DefaultSchemaFilesProviderTest makes PHPStan probe for a class of that name; PSR-4 resolves it
to the same file autoload.files already loaded, and the second include is fatal. The "parallel
worker" wording is a red herring — it's where the probe happens to land, not the cause.

The polyfill isn't needed in that test: getSchemaFiles() is a generator, so it's always
Traversable and the native iterator_to_array() accepts it on every supported version.
Asserting that first keeps level 8 happy about the declared iterable return type. It was the
only usage in the repo.

Worth fixing the autoload overlap in ibexa/polyfill-php82 too — any package importing that
function hits the same wall on 7.4 — but that shouldn't keep this branch red in the meantime. I
can open that separately if you'd like.

[Steveb-p]

Superseded by ibexa/polyfill-php82#7, which fixes the root cause rather than sidestepping it here.

The fatal came from ibexa/polyfill-php82 v1.0.1 listing src/iterator_to_array.php in both autoload.files and autoload.psr-4, with no function_exists() guard — so PHPStan probing the imported function as a class name included the file twice. #7 adds the guard, which fixes it for every package importing that function rather than just this one.

#42, #43 and #44 now carry a temporary dependencies.json pointing at that branch and are green on 7.4, so dropping the import here isn't needed.