minor #24723 [HttpFoundation] Mark new methods on Response as final (nicolas-grekas)

This PR was merged into the 3.4 branch.

Discussion
----------

[HttpFoundation] Mark new methods on Response as final

| Q             | A
| ------------- | ---
| Branch?       | 3.4
| Bug fix?      | no
| New feature?  | no
| BC breaks?    | no
| Deprecations? | no
| Tests pass?   | yes
| Fixed tickets | -
| License       | MIT
| Doc PR        | -

Commits
-------

a913f70583 [HttpFoundation] Mark new methods on Response as final

src/Symfony/Component/HttpFoundation/Response.php

@@ -612,6 +612,8 @@ class Response
      * @param bool $immutable enables or disables the immutable directive
      *
      * @return $this
+     *
+     * @final
      */
     public function setImmutable($immutable = true)
     {
@@ -628,6 +630,8 @@ class Response
      * Returns true if the response is marked as "immutable".
      *
      * @return bool returns true if the response is marked as "immutable"; otherwise false
+     *
+     * @final
      */
     public function isImmutable()
     {