fix: Use different API to detect readiness

Author: HofmeisterAn

src/Testcontainers.Pulsar/PulsarBuilder.cs

@@ -137,9 +137,8 @@ private static IReadOnlyDictionary<string, string> InitAuthenticationEnvVars()
     private sealed class WaitUntil : IWaitUntil
     {
         private readonly HttpWaitStrategy _httpWaitStrategy = new HttpWaitStrategy()
-            .ForPath("/admin/v2/clusters")
-            .ForPort(PulsarWebServicePort)
-            .ForResponseMessageMatching(IsClusterHealthyAsync);
+            .ForPath("/admin/v2/namespaces/public/default")
+            .ForPort(PulsarWebServicePort);
 
         private readonly bool _authenticationEnabled;