"x-elastic-product" header is not provided in 413 response

[mshustov]

Elasticsearch version: the nightly version
Related to #73424 cc @jbaiera

Description of the problem including expected versus actual behavior:
Kibana is in process of upgrading elasticsearch-js dependency. elastic/kibana#113950
The latest version of elasticsearch-js library checks x-elastic-product header presence in every response.
A Kibana integration test started suddenly failing because 413 Payload too large error response doesn't contain the header.

Steps to reproduce:

• install kibana repository
• check out on issue-108387-es-client-80 branch
• run yarn kbn bootstrap command
• run the test src/core/server/saved_objects/migrationsv2/integration_tests/batch_size_bytes_exceeds_es_content_length.test.ts

expected test passes
actual test fails with Error: Unable to complete saved object migrations for the [.kibana] index. ProductNotSupportedError: The client noticed that the server is not Elasticsearch and we do not support this unknown product.]

[elasticmachine]

Pinging @elastic/clients-team (Team:Clients)

[elasticmachine]

Pinging @elastic/es-data-management (Team:Data Management)

[rudolf]

Added the blocker label as this would be a release blocker for Kibana 8.0

[mshustov]

fixed in the ES client