Remove reference to kubernetesx

[VenelinMartinov]

Description

We no longer recommend using this.

Checklist:

• [ ] I have reviewed the style guide.
• [ ] If blogging, I have reviewed the blogging guide.
• [ ] I have manually confirmed that all new links work.
• [ ] I added aliases (i.e., redirects) for all filename changes.
• [ ] If making css changes, I rebuilt the bundle.

[pulumi-bot]

Your site preview for commit 57235638 is ready! :tada:

http://pulumi-hugo-origin-pr-4240-57235638.s3-website.us-west-2.amazonaws.com.

[github-actions[bot]]

Site previews for this pull request have been removed. ✨