2.0.0 silently dropped support for `grabFixture()` with numeric indices

https://github.com/Codeception/module-yii2/commit/baba62281f6839e1c21e646d50971156fd7b8faa, a typing refactoring, changed the type of `grabFixture()` `$index` param to `string|null`.

Historically though, this could also be an integer (like, if you just have a fixture array _without_ keys) - see e.g. https://github.com/yiisoft/yii2-app-advanced/blob/8d10c0d2ff1c78c454cf649226ca8465a198902e/frontend/tests/Support/data/login_data.php .

Imho that support should not be dropped. And if that was intentional, it should be in CHANGELOG / release notes.

(yes, technically, using integers as string `'0'` might still work, but that's ugly)