Update user_providers.rst

Adding return type to serveral functions

Author: hbgamra

security/user_providers.rst

@@ -328,7 +328,7 @@ command will generate a nice skeleton to get you started::
  *
  * @return UserInterface
  */
- public function refreshUser(UserInterface $user)
+ public function refreshUser(UserInterface $user): UserInterface
  {
  if (!$user instanceof User) {
  throw new UnsupportedUserException(sprintf('Invalid user class "%s".', get_class($user)));
@@ -342,7 +342,7 @@ command will generate a nice skeleton to get you started::
  /**
  * Tells Symfony to use this provider for this User class.
  */
- public function supportsClass(string $class)
+ public function supportsClass(string $class): bool
  {
  return User::class === $class || is_subclass_of($class, User::class);
  }