php 8.4 deprecations

These can be cleaned up easily with rector, but I don't know if they'd cause a BC break.

Deprecated: cebe\openapi\SpecBaseObject::resolveReferences(): Implicitly marking parameter $context as nullable is deprecated, the explicit nullable type must be used instead in /home/tac/sites/packages/vendor/cebe/php-openapi/src/SpecBaseObject.php on line 396

Deprecated: cebe\openapi\SpecObjectInterface::resolveReferences(): Implicitly marking parameter $context as nullable is deprecated, the explicit nullable type must be used instead in /home/tac/sites/packages/vendor/cebe/php-openapi/src/SpecObjectInterface.php on line 43

Deprecated: cebe\openapi\spec\Paths::resolveReferences(): Implicitly marking parameter $context as nullable is deprecated, the explicit nullable type must be used instead in /home/tac/sites/packages/vendor/cebe/php-openapi/src/spec/Paths.php on line 249

Deprecated: cebe\openapi\spec\PathItem::resolveReferences(): Implicitly marking parameter $context as nullable is deprecated, the explicit nullable type must be used instead in /home/tac/sites/packages/vendor/cebe/php-openapi/src/spec/PathItem.php on line 153

Deprecated: cebe\openapi\spec\Responses::resolveReferences(): Implicitly marking parameter $context as nullable is deprecated, the explicit nullable type must be used instead in /home/tac/sites/packages/vendor/cebe/php-openapi/src/spec/Responses.php on line 239

Deprecated: cebe\openapi\spec\Reference::__construct(): Implicitly marking parameter $to as nullable is deprecated, the explicit nullable type must be used instead in /home/tac/sites/packages/vendor/cebe/php-openapi/src/spec/Reference.php on line 72

Deprecated: cebe\openapi\spec\Reference::resolve(): Implicitly marking parameter $context as nullable is deprecated, the explicit nullable type must be used instead in /home/tac/sites/packages/vendor/cebe/php-openapi/src/spec/Reference.php on line 179

Deprecated: cebe\openapi\spec\Reference::resolveReferences(): Implicitly marking parameter $context as nullable is deprecated, the explicit nullable type must be used instead in /home/tac/sites/packages/vendor/cebe/php-openapi/src/spec/Reference.php on line 366

src/SpecBaseObject.php、src/SpecObjectInterface.php、および src/spec/Paths.php、PathItem.php、Responses.php、Reference.php にある resolveReferences とコンストラクターのシグネチャを確認してください。PHP 8.4 の非推奨化の挙動と、シグネチャの変更によって互換性が維持されるかを確認してください。報告された非推奨化が BC break なしで解消されれば完了です。

索引モデルが issue の本文から書いたものです。