docs: update collections table counts for data-science collection

## Component

Documentation

## Bug Description

The collection summary table in `docs/getting-started/collections.md` shows stale counts for the data-science collection after PR #1419 added `synth-data-generate.prompt.md`.

The table currently reads:

| Collection | Agents | Prompts | Instructions | Skills |
|---|---|---|---|---|
| data-science | 6 | **3** | **10** | 0 |

But `collections/data-science.collection.yml` now contains:

| Item type | Actual count |
|---|---|
| Agents | 6 |
| Prompts | **4** |
| Instructions | **9** |
| Skills | 0 |

The prompt count is off by 1 (the new `synth-data-generate.prompt.md` was not reflected), and the instruction count is also off by 1.

## Expected Behavior

The data-science row in `docs/getting-started/collections.md` should read:

```
| data-science | ... | 6 | 4 | 9 | 0 | Stable | ... |
```

## Steps to Reproduce

Introduced in commit `2f2edca` (PR #1419 — `feat(prompts): add synth-data-generate prompt to data-science collection`).

Count verification:

```bash
grep -E "kind: (agent|instruction|prompt|skill)" collections/data-science.collection.yml | sort | uniq -c
# Output: 6 agent, 9 instruction, 4 prompt
```

## Additional Context

- Documentation file: `docs/getting-started/collections.md` (line 38)
- Collection manifest: `collections/data-science.collection.yml`
- New prompt added: `.github/prompts/data-science/synth-data-generate.prompt.md`

> [!NOTE]
>
> 🔒 Integrity filter blocked 1 item
>
> The following item were blocked because they don't meet the GitHub integrity level.
>
> - [#435](https://github.com/microsoft/hve-core/issues/435) `search_issues`: has lower integrity than agent requires. The agent cannot read data with integrity below "approved".
>
> To allow these resources, lower `min-integrity` in your GitHub frontmatter:
>
> ```yaml
> tools:
> github:
> min-integrity: approved # merged | approved | unapproved | none
> ```
>
>

> Generated by [Documentation Update Check](https://github.com/microsoft/hve-core/actions/runs/24828210395/agentic_workflow) · ● 2.8M · [◷](https://github.com/search?q=repo%3Amicrosoft%2Fhve-core+is%3Aissue+%22gh-aw-workflow-call-id%3A+microsoft%2Fhve-core%2Fdoc-update-check%22&type=issues)

Start with the data-science row in docs/getting-started/collections.md and verify its values against collections/data-science.collection.yml. Run the grep command from the issue to confirm the 6 agent, 9 instruction, and 4 prompt counts. Done means the row shows 6, 4, 9, and 0 for the four item types.

Written by the indexing model from the issue text.