[Website]: Update default value of workflows:ui:enabled for version 9.4

### Before you submit

- [x] This issue is about a documentation page, flow, or piece of content.

### Type of issue

None

### What documentation page or section is affected

https://www.elastic.co/docs/reference/kibana/advanced-settings

### What happened?

## Issue:
As noted in [this document](https://www.elastic.co/docs/explore-analyze/workflows/authoring-techniques/migrate-from-9-3#workflows-whats-new-9.4), Workflows is enabled by default in 9.4 which makes `workflows:ui:enabled` defaults to `true`.
>Workflows is enabled by default. The workflows:ui:enabled advanced setting now defaults to true on deployments with the appropriate [subscription](https://www.elastic.co/pricing) in Elastic Stack or [project feature tier](https://www.elastic.co/docs/deploy-manage/deploy/elastic-cloud/project-settings) in Serverless.

However, the [Advanced settings](https://www.elastic.co/docs/reference/kibana/advanced-settings#kibana-general-settings:~:text=workflows%3Aui%3Aenabled) page still shows `Default: false`.

Moreover, `Workflows` is generally available since 9.4 and the labels are updated accordingly on pages such as [this](https://www.elastic.co/docs/explore-analyze/workflows).

However, the [Advanced settings](https://www.elastic.co/docs/reference/kibana/advanced-settings#kibana-general-settings:~:text=workflows%3Aui%3Aenabled) page still shows `Stack Preview 9.3+` only.

## Request:
Please update the [Advanced settings](https://www.elastic.co/docs/reference/kibana/advanced-settings#kibana-general-settings:~:text=workflows%3Aui%3Aenabled) document to show the current default value, `Default: true` and the current GA status, `Stack GA 9.4+` for the `workflows:ui:enabled` setting.

### Additional info

_No response_

---

## Elastic Docs AI Scoping 🤖

Docs issue scope

### Summary
The issue asks to update the [Advanced Settings reference page](https://www.elastic.co/docs/reference/kibana/advanced-settings) to reflect that `workflows:ui:enabled` now defaults to `true` and is GA in 9.4+. The `migrate-from-9-3.md` and `troubleshooting.md` pages in this repo already reflect the new default (`true`), confirming the Advanced Settings page is stale. Two additional pages in this repo also carry outdated lifecycle labels or instructions that imply manual opt-in is still required.

### Request accuracy
Accurate — `migrate-from-9-3.md` (line 206) and `troubleshooting.md` (line 368) both confirm the setting defaults to `true` as of 9.4.

### Next action for author
Update the `workflows:ui:enabled` entry on the Kibana Advanced Settings reference page (Kibana repo) and fix the two secondary pages in this repo.

### Impact: High

### Scope boundary
Only `workflows:ui:enabled` needs changing; no other Advanced Settings entries appear affected.

### Recommended documentation targets

| Page | URL | Action | Impact | Confidence | Why this page? |
|------|-----|--------|--------|------------|----------------|
| Kibana Advanced Settings reference | https://www.elastic.co/docs/reference/kibana/advanced-settings | Update existing page | High | High | Directly named in issue; source of the incorrect `Default: false` and `Stack Preview 9.3+` label |
| Elastic Security UI reference | https://www.elastic.co/docs/solutions/security/get-started/elastic-security-ui | Update existing page | Medium | High | `stack: preview 9.3+` applies-to tag and "turn on" admonition are stale for 9.4+ (`solutions/security/get-started/elastic-security-ui.md`, lines 140–146) |
| Build your first workflow (tutorial) | https://www.elastic.co/docs/explore-analyze/workflows/get-started/build-your-first-workflow | Update existing page | Medium | Medium | Prerequisites say "turn on the Elastic Workflows advanced setting" without noting it defaults to `true` in 9.4+ (`build-your-first-workflow.md`, line 22) |

### Recommendations

1. **Kibana repo** — Update the `workflows:ui:enabled` entry on the Advanced Settings reference page: change `Default: false` → `Default: true` and update the lifecycle label from `Stack Preview 9.3+` to `Stack GA 9.4+`.
2. **`solutions/security/get-started/elastic-security-ui.md`** — Change `stack: preview 9.3+` to `stack: preview 9.3, ga 9.4+` and update the admonition (line 146) to remove or qualify the "turn on" instruction for 9.4+ users (setting is on by default).
3. **`explore-analyze/workflows/get-started/build-your-first-workflow.md`** — Qualify the prerequisite on line 22: note that `workflows:ui:enabled` defaults to `true` in 9.4+ so manual activation is only required for 9.3.

### Notes

- The Kibana Advanced Settings page source is in the Kibana repository (`(reference/redacted) not in this repo — that change requires a Kibana-side PR.
- Items 2 and 3 are in this repo and can be addressed here.
- `setup.md` and `troubleshooting.md` are already up to date and do not need changes.

> Generated by [Issue Scope Analyzer](https://github.com/elastic/docs-content/actions/runs/27606768565) for issue #6894 · 212.8 AIC · ⌖ 17.7 AIC · ⊞ 29.3K · [◷](https://github.com/search?q=repo%3Aelastic%2Fdocs-content+is%3Aissue+%22gh-aw-workflow-call-id%3A+elastic%2Fdocs-content%2Fgh-aw-docs-issue-scope%22&type=issues)