Remove duplicated model for order document type

[windaishi]

Fixes Issue SW-20350

https://issues.shopware.com/issues/SW-20350

1. Why is this change necessary?

The model \Shopware\Models\Order\Document\Type is basically just an old and falsy version of \Shopware\Models\Document\Document.

It would make sense to remove it from the code. It's only real uses are here: /engine/Shopware/Models/Order/Repository.php#363 /engine/Shopware/Models/Order/Document/Document.php#121

2. What does this change do, exactly?

Removes the duplicated model \Shopware\Models\Order\Document\Type and replaces it's usages by the correct one (\Shopware\Models\Document\Document).

3. Describe each step to reproduce the issue or behaviour.

N/A

4. Please link to the relevant issues (if any).

https://issues.shopware.com/issues/SW-20350

5. Which documentation changes (if any) need to be made because of this PR?

None

6. Checklist

• [ ] I have written tests and verified that they fail without my change
• [x] I have squashed any insignificant commits
• [x] This change has comments for package types, values, functions, and non-obvious lines of code
• [x] I have read the contribution requirements and fulfil them.

[fixpunkt]

This one was closed, too: https://github.com/shopware/shopware/pull/1509

They said there that they already have an internal version of this, we shouldn't make a new version of this for 5.5.