Tests: Use new authenticatedAs option where useful

There are two more API integration tests that explicitly add the
"Authorization" header right now:

- `Flarum\Tests\integration\api\authentication\WithApiKeyTest`
- `Flarum\Tests\integration\api\csrf_protection\RequireCsrfTokenTest`

These two specifically test authentication, so in those cases the
explicitness seems desirable.

tests/integration/api/notifications/ListTest.php

@@ -24,9 +24,6 @@ class ListTest extends TestCase
             'users' => [
                 $this->normalUser(),
             ],
-            'access_tokens' => [
-                ['token' => 'normaltoken', 'user_id' => 2],
-            ],
         ]);
     }
 
@@ -48,8 +45,9 @@ class ListTest extends TestCase
     public function shows_index_for_user()
     {
         $response = $this->send(
-            $this->request('GET', '/api/notifications')
-                ->withHeader('Authorization', 'Token normaltoken')
+            $this->request('GET', '/api/notifications', [
+                'authenticatedAs' => 2,
+            ])
         );
 
         $this->assertEquals(200, $response->getStatusCode());