fix thumbnail link

Author: sidpalas

README.md

@@ -2,7 +2,7 @@
 
 This is the companion repo to: [GitHub Actions: Beginner to Pro](https://courses.devopsdirective.com/github-actions-beginner-to-pro)
 
-[![](./readme-assets/thumbnail-yt.png)]](https://youtu.be/Xwpi0ITkL3U)
+[![](./readme-assets/thumbnail-yt.png)](https://youtu.be/Xwpi0ITkL3U)
 
 ## 🙌 Sponsored by Namespace Labs