[Universal Profiling] Contradiction: xpack.profiling.enabled marked self: unavailable in Kibana YAML but self-managed setup docs exist

## Problem

There is a contradiction between the Kibana settings YAML and the docs-content page for enabling Universal Profiling in Kibana:

- **`profiling-settings.yml`** in the Kibana repo marks `xpack.profiling.enabled` as `self: unavailable`, and the setting description says "Available on {{ech}} only."
- **`step-2-enable-universal-profiling-in-kibana.md`** includes a [Self-managed Elastic stack section](https://www.elastic.co/docs/solutions/observability/infra-and-hosts/step-2-enable-universal-profiling-in-kibana#_self_managed_elastic_stack) with instructions to set this flag in `kibana.yml`. The page-level `applies_to` is `stack: ga` (which covers self-managed).

## What needs confirmation (from the profiling team)

Is Universal Profiling supported on self-managed deployments?

- **If yes**: the YAML's `self: unavailable` is wrong and needs updating to `self: ga` (or appropriate lifecycle tag).
- **If no**: the self-managed section in `step-2-enable-universal-profiling-in-kibana.md` should be removed, and the page-level `applies_to` should be updated to exclude self-managed.

## Context

Surfaced during the Observability advanced settings audit ([#4013](https://github.com/elastic/docs-content/issues/4013), [docs-content-internal#1636](https://github.com/elastic/docs-content-internal/issues/1636)). Flagged as out of scope for [PR #7986](https://github.com/elastic/docs-content/pull/7986) pending profiling team input.

Compare profiling-settings.yml with step-2-enable-universal-profiling-in-kibana.md, including its Self-managed Elastic stack section and page-level applies_to. Ask the profiling team to confirm whether self-managed deployments are supported; done when the YAML and documentation consistently reflect that decision, with the related audit issues and PR #7986 considered.

Written by the indexing model from the issue text.