[Security] Improve BC-layer to deprecate eraseCredentials methods

Author: nicolas-grekas

Tests/Fixtures/TestLegacyPasswordAuthenticatedUser.php

@@ -35,10 +35,9 @@ public function getRoles(): array
         return $this->roles;
     }
 
+    #[\Deprecated]
     public function eraseCredentials(): void
     {
-        // Do nothing
-        return;
     }
 
     public function getUserIdentifier(): string

Tests/Hasher/PasswordHasherFactoryTest.php

@@ -238,25 +238,9 @@ public function testMigrateFromWithCustomInstance()
 
 class SomeUser implements PasswordAuthenticatedUserInterface
 {
-    public function getRoles(): array
-    {
-    }
-
     public function getPassword(): ?string
     {
     }
-
-    public function getSalt(): ?string
-    {
-    }
-
-    public function getUserIdentifier(): string
-    {
-    }
-
-    public function eraseCredentials()
-    {
-    }
 }
 
 class SomeChildUser extends SomeUser