Change the way to reset the plain password after hashing it

The PasswordUpdater implementation resets the plain password to `null`
after hashing the password, marking the fact that a next code (done in a
Doctrine listener for instance) would not need to hash anything anymore.
Instead of relying on `UserInterface::eraseCredentials` which is
deprecated in Symfony 7.3+ and not guaranteed to implement this behavior
if the entity overrides the method, the `null` is now set explicitly.

Author: stof

src/Util/HashingPasswordUpdater.php

@@ -50,6 +50,6 @@ public function hashPassword(UserInterface $user): void
         }
 
         $user->setPassword($hashedPassword);
-        $user->eraseCredentials();
+        $user->setPlainPassword(null);
     }
 }