Remove duplicate --delay-enroll commands from Elastic Agent install command reference

[strawgate]

Remove duplicate --delay-enroll commands from Elastic Agent install command reference

[github-actions]

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[mergify]

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

• backport-/d./d is the label to automatically backport to the /d./d branch. /d is the digit
  NOTE: backport-skip has been added to this pull request.

[kilfoyle]

@strawgate Thanks for fixing this, and I'm sorry I didn't notice your PR until now!

Separately, I actually fixed the duplicates and some mis-orderings a few days ago (via this PR), so this one can be closed. Everything in the command ref should be okay now, but if I've missed anything please let me know.