[DOCS] Add deletion sub feature privilege for cases

[lcawl]

Relates to elastic/kibana#136996

Preview

https://security-docs_2219.docs-preview.app.elstc.co/guide/en/security/master/case-permissions.html

[mergify]

This pull request does not have a backport label. Could you fix it @lcawl? 🙏
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 creating this @lcawl !

I do have one question about the screenshot refresh: do you think it'd be useful to expand the Cases privs to show the sub-feature privs? Or is it better to keep that area collapsed since we'll likely add to it in the future?

[lcawl]

I do have one question about the screenshot refresh: do you think it'd be useful to expand the Cases privs to show the sub-feature privs?

I chose to leave it unexpanded since it's a subscription feature. However, if you disagree that's fine too. I also chose to not re-add the red boxes around the pertinent privileges, since we're generally trying to make screenshots that are easier to automate. If you prefer to have those boxes here and don't mind manually maintaining, that's fine too.

[benironside]

LGTM. Fwiw I think it's fine not to include the red boxes in the screenshot. The image is described well enough in text that I think users will find the relevant permissions without them.

[nastasha-solomon]

@lcawl ah ok, good to know and I'm totally fine not annotating the screenshot. I feel like the scope of the screenshot is limited enough that users can quickly locate where the privs are when they reference the image.