Add rate limiters information in OpenAPI documentation

[rndD]

Thread: https://clickhouse-inc.slack.com/archives/C08EJHG8EPR/p1752817172057079

We need to add info about our rate limiters in https://clickhouse.com/docs/cloud/manage/openapi?referrer=openapi-258755 and https://clickhouse.com/docs/cloud/manage/api/swagger