MINOR fix disable test (confluentinc#2382)

Author: rayokota

src/Confluent.SchemaRegistry/Rest/RestService.cs

@@ -238,8 +238,7 @@ private async Task<HttpResponseMessage> ExecuteOnOneInstanceAsync(Func<HttpReque
                     string message = "";
                     int errorCode = -1;
 
-                    // 4xx errors with valid SR error message as content should not be retried (these are conclusive).
-                    if ((int)response.StatusCode >= 400 && (int)response.StatusCode < 500)
+                    if (!IsRetriable((int)response.StatusCode))
                     {
                         try
                         {

test/Confluent.SchemaRegistry.Serdes.UnitTests/SerializeDeserialize.cs

@@ -27,6 +27,7 @@
 using Avro;
 using Avro.Generic;
 using Confluent.SchemaRegistry.Encryption;
+using Confluent.SchemaRegistry.Rules;
 
 
 namespace Confluent.SchemaRegistry.Serdes.UnitTests
@@ -325,6 +326,7 @@ public void ISpecificRecordCELFieldTransformDisable()
                 UseLatestVersion = true
             };
             RuleRegistry registry = new RuleRegistry();
+            registry.RegisterExecutor(new CelFieldExecutor());
             registry.RegisterOverride(new RuleOverride("CEL_FIELD", null, null, true));
             var serializer = new AvroSerializer<User>(schemaRegistryClient, config, registry);
             var deserializer = new AvroDeserializer<User>(schemaRegistryClient, null);