Typo fixes for DocumentManager arguments

| Q             | A
| ------------- | ---
| Doc fix?      | yes
| New docs?     | no
| Applies to    | 1.1 (at least)
| Fixed tickets | https://github.com/symfony-cmf/standard-edition/issues/13 (partly)

Documentation-only fixes of 3 specific cases where I found the import to be correct, and only the type hint wrong.

I'm happy to extend it to include more cases, so feedback is welcome about the specific way it needs to be done for each case (see [original issue](https://github.com/symfony-cmf/standard-edition/issues/13) for more information).