**Found in version**
- Observed in 8.2.3, but might exist longer

**Steps to reproduce**
On a multi node cloud cluster (might also work on a local multi node cluster):
- Create a transform with a retention policy
- Update the transform and remove the retention policy

**Expected result**
- The retention policy is removed

**Actual result**
- This sometimes results in an error:
```
An error occurred calling the API endpoint to update transforms.
Bad Request: [illegal_argument_exception: [illegal_argument_exception] Reason: 
Unknown NamedWriteable [org.elasticsearch.xpack.core.transform.transforms.RetentionPolicyConfig][null_retention_policy]]:
Unknown NamedWriteable [org.elasticsearch.xpack.core.transform.transforms.RetentionPolicyConfig][null_retention_policy]
```

**Additional information**
- Quote from slack discussion with @benwtrent:
  > It wouldn’t happen if you hit a node that can execute the update immediately without serializing to a different node
x-pack/plugin/core/src/main/java/org/elasticsearch/xpack/core/transform/TransformNamedXContentProvider.java
/*
 * Copyright Elasticsearch B.V. and/or licensed to Elasticsearch B.V. under one
 * or more contributor license agreements. Licensed under the Elastic License
 * 2.0; you may not use this file except in compliance with the Elastic License
 * 2.0.
 */
package org.elasticsearch.xpack.core.transform;
import org.elasticsearch.plugins.spi.NamedXContentProvider;
import org.elasticsearch.xcontent.NamedXContentRegistry;
import org.elasticsearch.xpack.core.transform.transforms.RetentionPolicyConfig;
import org.elasticsearch.xpack.core.transform.transforms.SyncConfig;
import org.elasticsearch.xpack.core.transform.transforms.TimeRetentionPolicyConfig;
import org.elasticsearch.xpack.core.transform.transforms.TimeSyncConfig;
import java.util.Arrays;
import java.util.List;
public class TransformNamedXContentProvider implements NamedXContentProvider {
    @Override
    public List<NamedXContentRegistry.Entry> getNamedXContentParsers() {
        return Arrays.asList(
            new NamedXContentRegistry.Entry(SyncConfig.class, TransformField.TIME, TimeSyncConfig::parse),
            new NamedXContentRegistry.Entry(RetentionPolicyConfig.class, TransformField.TIME, TimeRetentionPolicyConfig::parse)
        );
    }
}