[docs] Clean up cross-repo links

[colleenmcginnis]

Follow up to #6554

When using cross-repo links, the path should be relative to the docset.yml not the full path within the repo (updated docs-builder docs).

[github-actions]

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[mergify]

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

• v7.x is the label to automatically backport to the 7.x branch.
• v7./d./d is the label to automatically backport to the 7./d branch. /d is the digit

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

[nastasha-solomon]

Thanks for taking care of these links, @colleenmcginnis! I did some quick spot-checks and only noticed a few minor things. In addition to the comments that I left below, there is one other link that's not properly resolving in the preview:

Looks like a parentheses is missing from the end of the URL and we might need to move the text before the URL, e.g.:
[Date Math format](https://www.elastic.co/guide/en/elasticsearch/reference/current/common-options.html#date-math)

[colleenmcginnis]

Looks like a parentheses is missing from the end of the URL and we might need to move the text before the URL, e.g.:
Date Math format

Feel free to push a commit here or open another PR to fix other syntax issues!

[nastasha-solomon]

I can open a separate PR to fix the refs to the ES date time page. Thanks again for updating these links!