fix build

Author: sungam3r

src/GraphQL.Client/GraphQLHttpRequest.cs

@@ -41,7 +41,9 @@ public virtual HttpRequestMessage ToHttpRequestMessage(GraphQLHttpClientOptions
                 Content = new StringContent(serializer.SerializeToString(this), Encoding.UTF8, options.MediaType)
             };
 
+#pragma warning disable CS0618 // Type or member is obsolete
             PreprocessHttpRequestMessage(message);
+#pragma warning restore CS0618 // Type or member is obsolete
             return message;
         }
     }

tests/GraphQL.Integration.Tests/QueryAndMutationTests/Base.cs

@@ -173,7 +173,9 @@ public async void PreprocessHttpRequestMessageIsCalled()
             var callbackTester = new CallbackMonitor<HttpRequestMessage>();
             var graphQLRequest = new GraphQLHttpRequest($"{{ human(id: \"1\") {{ name }} }}")
             {
+#pragma warning disable CS0618 // Type or member is obsolete
                 PreprocessHttpRequestMessage = callbackTester.Invoke
+#pragma warning restore CS0618 // Type or member is obsolete
             };
 
             var defaultHeaders = StarWarsClient.HttpClient.DefaultRequestHeaders;