Say default queries are all in security-extended suite

[eroullit]

security-extended is an extension of the default queries (aka security), so any query in security is also in security-extended.

Why:

For some, it is unclear that the CodeQL security pack is contained in the security-extended pack though it is made very clear that security-extended is contained in security-and-quality.

What's being changed (if available, include any code snippets, screenshots, or gifs):

Check off the following:

• I have reviewed my changes in staging (look for the "Automatically generated comment" and click the links in the "Preview" column to view your latest changes).
• For content changes, I have completed the self-review checklist.

Writer impact (This section is for GitHub staff members only):

• This pull request impacts the contribution experience
  • I have added the 'writer impact' label
  • I have added a description and/or a video demo of the changes below (e.g. a "before and after video")

[welcome]

Thanks for opening this pull request! A GitHub docs team member should be by to give feedback soon. In the meantime, please check out the contributing guidelines.

[cmwilson21]

👋 @eroullit Thanks so much for opening a PR! I'll get this triaged for review ⚡

[felicitymay]

@eroullit - many thanks for this update to the docs ✨

You change is a great improvement in clarity 🚀

I'll approve the change and get this pull request ready to merge. Once merged, you should see your changes live within the next day.

[github-actions]

Thanks very much for contributing! Your pull request has been merged 🎉 You should see your changes appear on the site in approximately 24 hours. If you're looking for your next contribution, check out our help wanted issues ⚡