Removes noreferrer on explicit elastic.co domains

[joelgriffith]

Summary

This remove the noreferrer attribute on docsite links that are "known" elastic.co links. Here's the methodology I went through:

• Did a search of noreferrer in Kibana.
• Filtered out anything with snap in them (snapshots).
• Filtered out x-pack, but then added them in since it was easy enough.
• Links that either had explicit references, or implied, to elastic.co were whitelisted. I used my best judgement for the "implied" ones, so feel free to say "no" to them!

I'm anticipating some test failures, and will follow up accordingly, but wanted to get this out for review prior to investing more time in stability.

Checklist

Use strikethroughs to remove checklist items you don't feel are applicable to this PR.

• This was checked for cross-browser compatibility, including a check against IE11
• Any text added follows EUI's writing guidelines, uses sentence case text and includes i18n support
• Documentation was added for features that require explanation or tutorials
• Unit or functional tests were updated or added to match the most common scenarios

[elasticmachine]

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[peteharverson]

ML file edits LGTM

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[joelgriffith]

6.7 backport: #31326

[joelgriffith]

7.0 backport: #31327

[alexwizp]

@ogupte @peteharverson @epixa could you please check this PR, looks like it wasn't backported into 7.x.
As a result all versions between 7.0 and 8 still have noreferrer.

https://github.com/elastic/kibana/blob/7.x/src/legacy/core_plugins/kibana/server/ui_setting_defaults.js#L256

Partially it will be fixed when we make a backport of #66040 into 7.x but we fix that only for one file ui_setting_defaults.js