Small updates to AI page

[mit-mit]

Updated link to Flutter AI documentation and removed AI Toolkit section.

Description of what this PR is changing or adding, and why:

Issues fixed by this PR (if any):

PRs or commits this PR depends on (if any):

Presubmit checklist

• If you are unwilling, or unable, to sign the CLA, even for a tiny, one-word PR, please file an issue instead of a PR.
• If this PR is not meant to land until a future stable release, mark it as draft with an explanation.
• This PR follows the Google Developer Documentation Style Guidelines—for example, it doesn't use i.e. or e.g., and it avoids I and we (first-person pronouns).
• This PR uses semantic line breaks
  of 80 characters or fewer.

[gemini-code-assist]

Code Review

This pull request updates the AI page by modifying the MCP server link and text, and removing the 'ai-toolkit' section. A review comment correctly identifies a typo ('startes' instead of 'started') in the updated text and provides a suggestion to fix it.

[flutter-website-bot]

Staged preview of the updated docs.flutter.dev site (updated for commit b2cfaeb):

https://flutter-docs-prod--docs-pr13893-mit-mit-patch-1-00t31h6f.web.app

[flutter-website-bot]

Staged preview of the updated flutter.dev site (updated for commit b2cfaeb):

https://flutter-dev-230821--www-pr13893-mit-mit-patch-1-n2dk8ik2.web.app

[sfshaza2]

lgtm