test(provider): update ProbeTraitTest stub for split fetch API

The anonymous ProviderInterface implementation needs startFetch()/
resolveFetch() instead of fetch() to stay loadable.

tests/Unit/Service/Provider/ProbeTraitTest.php

@@ -31,7 +31,8 @@ final class ProbeTraitTest extends TestCase
             public function isConfigured(): bool { return $this->configured; }
             public function getName(): string { return 'test'; }
             public function ping(): void { ($this->ping)(); }
-            public function fetch(): array { return []; }
+            public function startFetch(): mixed { return null; }
+            public function resolveFetch(mixed $handle): array { return []; }
         };
     }