[HttpFoundation] [Response] replaced hard coded http status by constants

| Q             | A
| ------------- | ---
| Bug fix?      | [no]
| New feature?  | [no]
| BC breaks?    | [no]
| Deprecations? | [no]
| Tests pass?   | [yes]
| Fixed tickets | []
| License       | MIT
| Doc PR        | []

Http status were defined via constants but constants were not used in class so I replaced all calls to hard coded status by corresponding constant.

This is not an HTTP status code, it should not be publicly set as a constant like others.