docs: Update messaging pact docs to new API

docs/messaging-pacts.md

@@ -13,7 +13,7 @@ types use two different names, for example "Stock Broker API" and "Stock Broker
 Sample
 ------
 
-See the [sample](../samples/Messaging/) for additional detail.
+See the [sample](../samples/OrdersApi/) for additional detail.
 
 Consumer Tests
 --------------
@@ -26,24 +26,24 @@ In code, this is:
 ```csharp
 public class StockEventProcessorTests
 {
-    private readonly IMessagePactBuilderV3 messagePact;
+    private readonly IMessagePactBuilderV4 messagePact;
 
     public StockEventProcessorTests(ITestOutputHelper output)
     {
-        IPactV3 v3 = Pact.V3("Stock Event Consumer", "Stock Event Producer", new PactConfig
+        IPactV4 v4 = Pact.V4("Stock Event Consumer", "Stock Event Producer", new PactConfig
         {
             PactDir = "../../../pacts/",
-            DefaultJsonSettings = new JsonSerializerSettings
+            DefaultJsonSettings = new JsonSerializerOptions
             {
-                ContractResolver = new CamelCasePropertyNamesContractResolver()
+                PropertyNamingPolicy = JsonNamingPolicy.CamelCase
             },
             Outputters = new[]
             {
                 new XUnitOutput(output)
             }
         });
 
-        this.messagePact = v3.WithMessageInteractions();
+        this.messagePact = v4.WithMessageInteractions();
     }
 
     [Fact]