[FrameworkBundle] Changed hard coded value to Response class constant (302)

This PR was submitted on the symfony/FrameworkBundle read-only repository and moved automatically to the main Symfony repository (closes symfony/FrameworkBundle#9).

Replaced hard coded parameter value (code = 302) in redirect method by its equivalent value in Response object constants

| Q             | A
| ------------- | ---
| Bug fix?      | no
| New feature?  | no
| BC breaks?    | no
| Tests pass?   | yes
| License       | MIT