Removed Markdown Ninja Announcement

Removed the announcement about Markdown Ninja, as it doesn't appear to have anything to do with writing Rust code, and it isn't written in Rust (it's written in Go and Vue mostly).

Author: chris-t-jansen

content/2025-05-21-this-week-in-rust.md

@@ -39,7 +39,6 @@ and just ask the editors to select the category.
 * [Celebrating Rust’s Birthday with Karen Tölva: Creator of Ferris the Rustacean!](https://rustfoundation.org/media/celebrating-rusts-birthday-with-karen-tolva-creator-of-ferris-the-rustacean/)
 
 ### Project/Tooling Updates
-* [Announcing Markdown Ninja: Open Source alternative to Substack, Mailchimp and Netlify](https://kerkour.com/announcing-markdown-ninja)
 * [Hypervisor as a Library](https://seiya.me/blog/hypervisor-as-a-library)
 
 ### Observations/Thoughts