fix(walkthrough): update help link for LocalStack

[gtsiolis]

Problem

In the Application Builder walkthrough ("Complete installation" step), the LocalStack Learn more link renders as raw markdown text instead of a clickable link:

[Learn more]((https://docs.localstack.cloud/aws/).

The link target has a doubled opening parenthesis ((, which breaks VS Code's markdown rendering. The Finch entry just below renders correctly, so the two optional-tool entries look inconsistent and the LocalStack docs are unreachable.

This affects the macOS/Linux variant of AWS.toolkit.lambda.walkthrough.toolInstall.description; the .windows variant was already correct.

Solution

• Remove the extra ( so the LocalStack link renders as a clickable Learn more.
• Drop the trailing period and align spacing so the entry matches the Finch entry.

Applied to both the default and .windows variants in packages/core/package.nls.json. The packages/toolkit/ copies are
generated from this file at build time (copyFiles), so no manual edits there.

Before / After

Before	After

---

• Treat all work as PUBLIC. Private feature/x branches will not be squash-merged at release time.
• Your code changes must meet the guidelines in CONTRIBUTING.md.
• License: I confirm that my contribution is made under the terms of the Apache 2.0 license.

[amazon-inspector-ohio]

⏳ I'm reviewing this pull request for security vulnerabilities and code quality issues. I'll provide an update when I'm done

[amazon-inspector-ohio]

✅ I finished the code review, and didn't find any security or code quality issues.

[gtsiolis]

@valerena since you added the original LocalStack walkthrough, could you or someone from the team take a look? 😁

Cc @laileni-aws because of #8229