[8.15](backport #4247) Remove mention of new experience

[mergify]

The new experience isn't available in 8.15, so I'm removing this mention and will add it for 8.16.

---

This is an automatic backport of pull request #4247 done by Mergify.

[mergify]

Cherry-pick of c3186ed has failed:

On branch mergify/bp/8.15/pr-4247
Your branch is up to date with 'origin/8.15'.

You are currently cherry-picking commit c3186edc.
  (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)

Changes to be committed:
	modified:   docs/en/observability/logs-add-service-name.asciidoc

Unmerged paths:
  (use "git add/rm <file>..." as appropriate to mark resolution)
	deleted by us:   docs/en/serverless/logging/add-logs-service-name.mdx

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

[github-actions]

A documentation preview will be available soon.

• 🔨 Buildkite builds
• 📚 HTML diff
• 📙 Preview page

Request a new doc build by commenting

• Rebuild this PR: run docs-build
• Rebuild this PR and all Elastic docs: run docs-build rebuild

_{run docs-build is much faster than run docs-build rebuild. A rebuild should only be needed in rare situations.}

_{If your PR continues to fail for an unknown reason, the doc build pipeline may be broken. Elastic employees can check the pipeline status here.}