added warning for required privileges

[robb3rt]

Adjusted the document to ensure alignment and correctness after following changes were made: #81400
and adjusted for proposed solution mentioned here: #81451 (comment)

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[elasticsearchmachine]

@robb3rt please enable the option "Allow edits and access to secrets by maintainers" on your PR. For more information, see the documentation.

[elasticmachine]

Pinging @elastic/es-docs (Team:Docs)

[lockewritesdocs]

Suggested change

	IMPORTANT: This action deletes system indices and [starting from 8.1](https://github.com/elastic/elasticsearch/pull/81400) system index write-access has been removed from the superuser role. So, if you are performing this action from a user with the superuser role, you need to ensure that the user has another role with the `allow_restricted_indices` set to `true` to be able to delete all system indices.
	IMPORTANT: This action deletes system indices. In {es} 8.1 and later, the superuser
	role doesn't have write access to system indices. If you execute this request as a
	user with the superuser role, you must have an additional role with the
	`allow_restricted_indices` privilege set to `true` to delete all system indices.

[lockewritesdocs]

Here's a suggested rewording of your original text. Let me know if this change makes sense 💡

[abdonpijpelink]

@robb3rt Are you interested in continuing to work on this PR, and apply the suggestion in #88438 (comment)? Otherwise, we'd be happy to take it from here.

[leemthompo]

Important

Elastic documentation is migrating to Markdown for version 9.0+. See the migration guide for details.

ℹ️ What's happening?

• Starting January 29, we will start closing all unmerged documentation PRs targeting main/master
• We're migrating from AsciiDoc to Markdown for 9.0+
• 9.0 docs will be frozen from January 29 until February 20 2024
• NOTE: PRs that include both code and documentation changes will remain open

What do I need to do?

For <=8.x docs:

1. Rebase your PR to target the relevant 8.x branch instead
2. The content can remain in AsciiDoc format

For 9.0+ docs:

Option 1:

• Draft docs in Markdown
• Once migration freeze ends, find the relevant page in the new docs system and use the edit options to submit your changes

Option 2:

• Open an issue in elastic/docs-content

💡 Need help?

1. For Elasticians: Ask in #docs Slack channel
2. For external contributors: Open an issue in elastic/docs-content