docs: remove broken links

Signed-off-by: Romain Lespinasse <romain.lespinasse@gmail.com>

README.md

@@ -96,7 +96,6 @@ In English :gb:
 - [Action spotlight by Michael Heap][article-2]
 - [Serverless Deploy Previews on GitHub Actions][article-3]
 - [Let's Build a Continuous Delivery and Branching Process with GitHub Actions, Vercel and Heroku][article-4]
-- [Celebrating 5 Years of github-slug-action on sfeir.dev][article-7]
 
 In French :fr:
 
@@ -124,5 +123,4 @@ In Chinese :cn:
 [article-4]: https://javascript.plainenglish.io/lets-build-a-continuous-delivery-and-branching-process-c27dae09f0b6
 [article-5]: https://eryajf.github.io/HowToStartOpenSource/views/03-github-tips/10-Use-github-slug-action-to-leak-key-variables-in-the-Github-Action-context.html
 [article-6]: https://www.sfeir.dev/5-ans-de-github-slug-action-une-aventure-open-source/
-[article-7]: https://www.romainlespinasse.dev/posts/celebrating-5-years-of-github-slug-action/
 [talk-1]: https://www.youtube.com/watch?v=F5mBDmOQcvE