docs: update test plan

[endorama]

Motivation/summary

Update test plan to reflect recent changes.

Checklist

• [N/A] Update CHANGELOG.asciidoc
• [N/A] 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

Review the content, is not possible to review the rendered markdown before merging to main.

Related issues

Closes #12996

[mergify]

This pull request does not have a backport label. Could you fix it @endorama? 🙏
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.