test: restore MaxAgeMs values in cluster tests after timestamp fix

Now that MemStore uses Unix epoch timestamps (13a3f81), restore the
original Go MaxAge values that were previously omitted as workarounds:
- JsCluster2: MaxAgeMs=500 (Go: 500ms)
- JsCluster34: MaxAgeMs=5000 (Go: 5s)

tests/NATS.Server.Tests/JetStream/Cluster/JsCluster34GoParityTests.cs

@@ -28,13 +28,16 @@ public class JsCluster34GoParityTests
         // Go: TestJetStreamClusterStreamMaxAgeScaleUp — jetstream_cluster_3_test.go:3001
         // After scale-up the replica group is re-created with the new replica count.
         // Messages published before scale-up must still be present.
-        // Note: MaxAgeMs is omitted because the .NET MemStore uses Ticks*100 nanosecond
-        // timestamps that overflow long, causing immediate message expiration in tests.
-        // The core behavior under test is that messages survive scale-up.
+        // Go: MaxAge = 5s
         await using var cluster = await JetStreamClusterFixture.StartAsync(3);
 
-        // Use CreateStreamAsync (MaxAgeMs=0, no pruning) to test scale-up message preservation.
-        var createResp = await cluster.CreateStreamAsync("SCALEAGE", ["sa.>"], replicas: 1);
+        var createResp = cluster.CreateStreamDirect(new StreamConfig
+        {
+            Name = "SCALEAGE",
+            Subjects = ["sa.>"],
+            Replicas = 1,
+            MaxAgeMs = 5_000,
+        });
         createResp.Error.ShouldBeNull();
 
         for (var i = 0; i < 10; i++)