DAOS-18650 docs: Update pre-deployment doc to mandate sysctl for UCX.

[jgmoore-or]

Steps for the author:

• Commit message follows the guidelines.
• Appropriate Features or Test-tag pragmas were used.
• Appropriate Functional Test Stages were run.
• At least two positive code reviews including at least one code owner from each category referenced in the PR.
• Testing is complete. If necessary, forced-landing label added and a reason added in a comment.

After all prior steps are complete:

• Gatekeeper requested (daos-gatekeeper added as a reviewer).

[github-actions]

Ticket title is 'Predeployment checklist states sysctl setup applies to verbs provider; these also apply for UCX providers.'
Status is 'In Review'
Errors are Unknown component
https://daosio.atlassian.net/browse/DAOS-18650