minor #51500 Remove getUsername methods in tests (alamirault)

This PR was merged into the 7.0 branch.

Discussion
----------

Remove `getUsername` methods in tests

| Q             | A
| ------------- | ---
| Branch?       | 7.0
| Bug fix?      | no
| New feature?  | no
| Deprecations? | no
| Tickets       | N/A
| License       | MIT
| Doc PR        | N/A

This is allowed thanks to bumps to `^6.4|^7.0` in composer.json on 7.0 branch

Commits
-------

85cafd35ac Remove getUsername methods in tests

Author: fabpot

Tests/Fixtures/TestLegacyPasswordAuthenticatedUser.php

@@ -41,11 +41,6 @@ public function eraseCredentials(): void
         return;
     }
 
-    public function getUsername(): string
-    {
-        return $this->username;
-    }
-
     public function getUserIdentifier(): string
     {
         return $this->username;

Tests/Hasher/PasswordHasherFactoryTest.php

@@ -199,10 +199,6 @@ public function getSalt(): ?string
     {
     }
 
-    public function getUsername(): string
-    {
-    }
-
     public function getUserIdentifier(): string
     {
     }