Update Password facade docblock (#44968)

Co-authored-by: Francis Mawn <[email protected]>

Author: FrankMawn

src/Illuminate/Support/Facades/Password.php

@@ -7,7 +7,7 @@
 /**
  * @method static mixed reset(array $credentials, \Closure $callback)
  * @method static string sendResetLink(array $credentials, \Closure $callback = null)
- * @method static \Illuminate\Contracts\Auth\CanResetPassword getUser(array $credentials)
+ * @method static \Illuminate\Contracts\Auth\CanResetPassword|null getUser(array $credentials)
  * @method static string createToken(\Illuminate\Contracts\Auth\CanResetPassword $user)
  * @method static void deleteToken(\Illuminate\Contracts\Auth\CanResetPassword $user)
  * @method static bool tokenExists(\Illuminate\Contracts\Auth\CanResetPassword $user, string $token)