fix typo in 2026-08-28-htmx-4.0.0-is-released.md

[dangbert]

Description

one char typo in docs

Corresponding issue:

Testing

Please explain how you tested this change manually, and, if applicable, what new tests you added. If
you're making a change to just the website, you can omit this section.

Checklist

• I have read the contribution guidelines
• I have targeted this PR against the correct branch (master for website changes, dev for
  source changes)

I think four-dev might actually by the right branch based on the "Edit page" hyperlink in the article itself.

• This is either a bugfix, a documentation update, or a new feature that has been explicitly
  approved via an issue
• I ran the test suite locally (npm run test) and verified that it succeeded