### Elasticsearch Version

main

### Installed Plugins

_No response_

### Java Version

_bundled_

### OS Version

MacOS

### Problem Description

When there are 2 or more concurrent `_update` requests issued, one of them may fail with `ResourceAlreadyExistsException` exception which is misleading.


### Steps to Reproduce

1. Spawn a number of `_update` requests at the same time
2. Look at the results of these requests
3. Observe `ResourceAlreadyExistsException` being thrown in the case of conflict

### Logs (if relevant)

_No response_
x-pack/plugin/transform/qa/single-node-tests/src/javaRestTest/java/org/elasticsearch/xpack/transform/integration/TransformUpdateIT.java
setupUser(TEST_ADMIN_USER_NAME_NO_DATA, List.of("transform_admin"));
        createReviewsIndex();
    }
    @SuppressWarnings("unchecked")
    public void testUpdateDeprecatedSettings() throws Exception {
        String transformId = "old_transform";
        String transformDest = transformId + "_idx";
        setupDataAccessRole(DATA_ACCESS_ROLE, REVIEWS_INDEX_NAME, transformDest);
        final Request createTransformRequest = createRequestWithAuth(
            "PUT",
            getTransformEndpoint() + transformId,
            BASIC_AUTH_VALUE_TRANSFORM_ADMIN_1
        );
        String config = Strings.format("""
            {
              "dest": {
                "index": "%s"
              },
              "source": {
                "index": "%s"
              },
              "pivot": {
                "group_by": {
                  "reviewer": {
                    "terms": {
                      "field": "user_id"
                    }
                  }
                },
                "aggregations": {