minor [Serializer] Fix CS. Uniformize PHPDoc.

| Q             | A
| ------------- | ---
| Bug fix?      | no
| New feature?  | no
| BC breaks?    | no
| Deprecations? | no
| Tests pass?   | yes
| License       | MIT
This is useless as it does not add any more value than the method signature. Should be removed. Can you do the same where this is the same situation in this PR?