minor #24391 Remove remaining @experimental annotations (nicolas-grekas)

This PR was merged into the 3.4 branch.

Discussion
----------

Remove remaining `@experimental` annotations

| 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        | -

Our policy states that experimental features should be either be deprecated or go mainstream in the next minor.
I propose to make all current ones mainstream.

Commits
-------

17a413876a Remove remaining `@experimental` annotations

src/Symfony/Bundle/SecurityBundle/DependencyInjection/Security/Factory/JsonLoginFactory.php

@@ -19,8 +19,6 @@ use Symfony\Component\DependencyInjection\Reference;
  * JsonLoginFactory creates services for JSON login authentication.
  *
  * @author Kévin Dunglas <dunglas@gmail.com>
- *
- * @experimental in version 3.3
  */
 class JsonLoginFactory extends AbstractFactory
 {

src/Symfony/Component/Cache/CacheItem.php

@@ -135,8 +135,6 @@ final class CacheItem implements CacheItemInterface
      * Returns the list of tags bound to the value coming from the pool storage if any.
      *
      * @return array
-     *
-     * @experimental in version 3.3
      */
     public function getPreviousTags()
     {

src/Symfony/Component/Security/Http/Firewall/UsernamePasswordJsonAuthenticationListener.php

@@ -39,8 +39,6 @@ use Symfony\Component\Security\Http\SecurityEvents;
  * an authentication via a JSON document composed of a username and a password.
  *
  * @author Kévin Dunglas <dunglas@gmail.com>
- *
- * @experimental in version 3.3
  */
 class UsernamePasswordJsonAuthenticationListener implements ListenerInterface
 {