minor symfony#48414 [Security] Add missing deprecations to UPGRADE-6.2.md file (moismailzai)

This PR was submitted for the 6.3 branch but it was merged into the 6.2 branch instead.

Discussion
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[Security] Add missing deprecations to `UPGRADE-6.2.md` file

| Q             | A
| ------------- | ---
| Branch?       | 6.2
| Bug fix?      | no
| New feature?  | no
| Deprecations? | yes
| Tickets       | n/a
| License       | MIT
| Doc PR        | n/a

Add a note about a deprecated property and its replacement.

note the deprecation to `Security::LAST_USERNAME`

Commits
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591e5cd Update UPGRADE-6.2.md

Author: OskarStark

UPGRADE-6.2.md

@@ -86,6 +86,10 @@ Security
  * Add maximum username length enforcement of 4096 characters in `UserBadge` to
    prevent [session storage flooding](https://symfony.com/blog/cve-2016-4423-large-username-storage-in-session)
  * Deprecate the `Symfony\Component\Security\Core\Security` class and service, use `Symfony\Bundle\SecurityBundle\Security\Security` instead
+ * Deprecate the `Symfony\Bundle\SecurityBundle\Security\Security::ACCESS_DENIED_ERROR` property, use `Symfony\Component\Security\Http\SecurityRequestAttributes::ACCESS_DENIED_ERROR` instead
+ * Deprecate the `Symfony\Bundle\SecurityBundle\Security\Security::AUTHENTICATION_ERROR` property, use `Symfony\Component\Security\Http\SecurityRequestAttributes::AUTHENTICATION_ERROR` instead
+ * Deprecate the `Symfony\Bundle\SecurityBundle\Security\Security::LAST_USERNAME` property, use `Symfony\Component\Security\Http\SecurityRequestAttributes::LAST_USERNAME` instead
+ * Deprecate the `Symfony\Bundle\SecurityBundle\Security\Security::MAX_USERNAME_LENGTH` property, use `Symfony\Component\Security\Http\Authenticator\Passport\Badge\UserBadge::MAX_USERNAME_LENGTH` instead
  * Passing empty username or password parameter when using `JsonLoginAuthenticator` is not supported anymore
  * Add `$lifetime` parameter to `LoginLinkHandlerInterface::createLoginLink()`
  * Change the signature of `TokenStorageInterface::setToken()` to `setToken(?TokenInterface $token)`