Fix unit tests: use mock gRPC client to avoid network calls

Author: mpartipilo

src/Weaviate.Client.Managed.Tests/Mocks/MockWeaviateClient.cs

@@ -30,14 +30,12 @@ public static (WeaviateClient Client, MockHttpMessageHandler Handler) CreateWith
             }
         );
 
-        var config = new ClientConfiguration
-        {
-            RestAddress = "localhost",
-            GrpcAddress = "localhost",
-            HttpMessageHandler = mockHandler,
-        };
+        // Create a no-op gRPC channel to avoid network calls
+        var grpcChannel = NoOpGrpcChannel.Create();
+        var grpcClient = new Grpc.WeaviateGrpcClient(grpcChannel);
 
-        var client = new WeaviateClient(config);
+        // Pass the mock gRPC client to avoid health check failures
+        var client = new WeaviateClient(httpMessageHandler: mockHandler, grpcClient: grpcClient);
 
         return (client, mockHandler);
     }