refactor: update GitHub Skills link to point to the GitHub Learn URL (#75)

Author: FidelusAleksander

markdown-templates/readme/exercise-finished.md

@@ -25,7 +25,7 @@
 **Keep the momentum going!**
 
 [![](https://img.shields.io/badge/Return%20to%20Exercise-%E2%86%92-1f883d?style=for-the-badge&logo=github&labelColor=197935)]({{{ issue_url }}})
-[![GitHub Skills](https://img.shields.io/badge/Explore%20GitHub%20Skills-000000?style=for-the-badge&logo=github&logoColor=white)](https://skills.github.com)
+[![GitHub Skills](https://img.shields.io/badge/Explore%20GitHub%20Skills-000000?style=for-the-badge&logo=github&logoColor=white)](https://learn.github.com/skills))
 
 *There's no better way to learn than building things!* 🚀