### 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
private static final String TEST_USER_NAME = "transform_user";
    private static final String BASIC_AUTH_VALUE_TRANSFORM_USER = basicAuthHeaderValue(TEST_USER_NAME, TEST_PASSWORD_SECURE_STRING);
    private static final String TEST_ADMIN_USER_NAME_1 = "transform_admin_1";
    private static final String BASIC_AUTH_VALUE_TRANSFORM_ADMIN_1 = basicAuthHeaderValue(
        TEST_ADMIN_USER_NAME_1,
        TEST_PASSWORD_SECURE_STRING
    );
    private static final String TEST_ADMIN_USER_NAME_2 = "transform_admin_2";
    private static final String BASIC_AUTH_VALUE_TRANSFORM_ADMIN_2 = basicAuthHeaderValue(
        TEST_ADMIN_USER_NAME_2,
        TEST_PASSWORD_SECURE_STRING
    );