Update monitor-apm-server.asciidoc

[kruskall]

correction: switch ECE and ESS (was inverted)

Motivation/summary

Reopened #10901 and targeting main.
Mostly two reasons:

• PR was targeting 8.8
• Rebasing on 8.10 failed to CLA check (???)

Checklist

- [ ] Update CHANGELOG.asciidoc
- [ ] Update package changelog.yml (only if changes to apmpackage have been made)
- [ ] Documentation has been updated

For functional changes, consider:

• Is it observable through the addition of either logging or metrics?
• Is its use being published in telemetry to enable product improvement?
• Have system tests been added to avoid regression?

How to test these changes

Related issues

[mergify]

This pull request does not have a backport label. Could you fix it @kruskall? 🙏
To fixup this pull request, you need to add the backport labels for the needed
branches, such as:

• backport-7.17 is the label to automatically backport to the 7.17 branch.
• backport-8./d is the label to automatically backport to the 8./d branch. /d is the digit.

NOTE: backport-skip has been added to this pull request.

[kruskall]

CLA was flaky and complained about a commit pushed one of our bot/machine accounts (???)