[8.19] (backport #7442) Update CODEOWNERS

[mergify]

What does this PR do?

We are deprecating the GH team called ingest-eng-prod:

For such, we are now using two GH teams:

• @elastic/observablt-ci
• @elastic/observablt-ci-contractors

The error is expected in the CODEOWNERS, the permissions will be changed in a follow-up

Why is it important?

Removing old references

Checklist

• I have read and understood the pull request guidelines of this project.
• My code follows the style guidelines of this project
• I have commented my code, particularly in hard-to-understand areas
• I have made corresponding changes to the documentation
• I have made corresponding change to the default configuration files
• I have added tests that prove my fix is effective or that my feature works
• I have added an entry in ./changelog/fragments using the changelog tool
• I have added an integration test or an E2E test

Disruptive User Impact

How to test this PR locally

Related issues

Questions to ask yourself

• How are we going to support this in production?
• How are we going to measure its adoption?
• How are we going to debug this?
• What are the metrics I should take care of?
• ...

---

This is an automatic backport of pull request #7442 done by [Mergify](https://mergify.com).

[mergify]

Cherry-pick of 8af30b0 has failed:

On branch mergify/bp/8.19/pr-7442
Your branch is up to date with 'origin/8.19'.

You are currently cherry-picking commit 8af30b0f7.
  (fix conflicts and run "git cherry-pick --continue")
  (use "git cherry-pick --skip" to skip this patch)
  (use "git cherry-pick --abort" to cancel the cherry-pick operation)

Unmerged paths:
  (use "git add <file>..." to mark resolution)
	both modified:   .github/CODEOWNERS

no changes added to commit (use "git add" and/or "git commit -a")

To fix up this pull request, you can check it out locally. See documentation: https://docs.github.com/en/pull-requests/collaborating-with-pull-requests/reviewing-changes-in-pull-requests/checking-out-pull-requests-locally