Swift CI tutorial examples are outdated (Swift 5.2/5.3, setup-swift pinned to a 2021 commit)

### Code of Conduct

- [x] I have read and agree to the GitHub Docs project's [Code of Conduct](https://github.com/github/docs/blob/main/.github/CODE_OF_CONDUCT.md)

### What article on docs.github.com is affected?

[Building and testing Swift](https://docs.github.com/en/actions/tutorials/build-and-test-code/swift)

Source file: `content/actions/tutorials/build-and-test-code/swift.md`

### What part(s) of the article would you like to see updated?

The tutorial's examples have aged and no longer reflect current Swift CI practice:

- **Swift versions are several years old.** The matrix example uses `swift: ["5.2", "5.3"]` and the single-version examples use `"5.3.3"`. Swift is now on the 6.x series (current release 6.3).
- **`swift-actions/setup-swift` is pinned to a 2021 commit** (`65540b95f51493d65f5e59e97dcef9629ddf11bf`). The action's current release is v2.4.0 (November 2025). This is the same kind of staleness previously reported in #12678.

#### Proposed changes (the uncontroversial refresh)

1. Update the example Swift versions to current releases.
2. Refresh the `swift-actions/setup-swift` SHA pin to its current release, keeping the not-certified-by-GitHub notice and SHA-pinning reusables already used on the page.
3. Optionally add a short section showing how to build and test on Linux using the official `swift` container images (and the `swiftlang/swift` nightly images), which doesn't require a separate Swift-setup step.

#### A question before I open a PR

Swift CI today commonly spans more than Ubuntu/macOS `swift build` — Apple platforms via Xcode, plus Windows, Android, and WebAssembly. Would the team be open to a brief cross-platform section that demonstrates these, including links to community actions (for example `compnerd/gha-setup-swift` for Windows and `skiptools/swift-android-action` for Android)?

I'd like to confirm this fits the docs' guidance on mentioning third-party tools before investing in a larger PR. For transparency: one action I might reference, `brightdigit/swift-build`, is one I maintain, so I'd want any mention to be neutral and in line with how the page already references `swift-actions/setup-swift`.

Happy to scope the PR to just items 1–2 (or 1–3) if that's preferable.

### Additional information

_No response_

Start with content/actions/tutorials/build-and-test-code/swift.md and review the existing Swift version matrix, single-version examples, and setup-swift SHA pin. Confirm the intended scope before changing the optional cross-platform material; done means the examples use current Swift releases, the action pin is refreshed, and the existing notices and reusable guidance remain intact.

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