(DOCS-3927) Update PS uninstall instructions

[hestonhoffman]

I tested the replacement PS script out on a Windows machine and it works fine (as long as WinRM is configured).

I added tabs and made some other quick fixes while I was in there.

Reviewer checklist

• [ ] Review the changed files.
• [ ] Review the URLs listed in the Preview section.
• [ ] Check images for PII
• [ ] Review any mentions of "Contact Datadog support" for internal support documentation.

[github-actions[bot]]

Preview links (active after the build_preview check completes)

Modified Files

• https://docs-staging.datadoghq.com/heston/DOCS-3927/agent/guide/how-do-i-uninstall-the-agent