minor #31813 fix type hint for salt in PasswordEncoderInterface (garak)

This PR was squashed before being merged into the 3.4 branch (closes #31813).

Discussion
----------

fix type hint for salt in PasswordEncoderInterface

See issue #31812

| Q             | A
| ------------- | ---
| Branch?       | 3.4
| Bug fix?      | yes
| New feature?  | no
| BC breaks?    | no
| Deprecations? | no
| Tests pass?   | yes
| Fixed tickets | #31812
| License       | MIT
| Doc PR        | none

Pretty self-explanatory

Commits
-------

0e741f9600 fix type hint for salt in PasswordEncoderInterface

src/Symfony/Component/Security/Core/Encoder/BasePasswordEncoder.php

@@ -48,8 +48,8 @@ abstract class BasePasswordEncoder implements PasswordEncoderInterface
     /**
      * Merges a password and a salt.
      *
-     * @param string $password The password to be used
-     * @param string $salt     The salt to be used
+     * @param string      $password The password to be used
+     * @param string|null $salt     The salt to be used
      *
      * @return string a merged password and salt
      *

src/Symfony/Component/Security/Core/Encoder/PasswordEncoderInterface.php

@@ -23,8 +23,8 @@ interface PasswordEncoderInterface
     /**
      * Encodes the raw password.
      *
-     * @param string $raw  The password to encode
-     * @param string $salt The salt
+     * @param string      $raw  The password to encode
+     * @param string|null $salt The salt
      *
      * @return string The encoded password
      *
@@ -36,9 +36,9 @@ interface PasswordEncoderInterface
     /**
      * Checks a raw password against an encoded password.
      *
-     * @param string $encoded An encoded password
-     * @param string $raw     A raw password
-     * @param string $salt    The salt
+     * @param string      $encoded An encoded password
+     * @param string      $raw     A raw password
+     * @param string|null $salt    The salt
      *
      * @return bool true if the password is valid, false otherwise
      *