Remove broken link (#9175)

The video link about unit tests was broken. (The video was made privated by the user.)

Co-authored-by: Kamran Ahmed <kamranahmed.se@gmail.com>

src/data/roadmaps/backend/content/unit-testing@3OYm6b9f6WOrKi4KTOZYK.md

@@ -6,5 +6,5 @@ Visit the following resources to learn more:
 
 - [@article@Unit Testing](https://en.wikipedia.org/wiki/Unit_testing)
 - [@article@What is Unit Testing?](https://www.guru99.com/unit-testing-guide.html)
-- [@video@What is Unit Testing?](https://www.youtube.com/watch?v=W2KOSaetWBk)
+- [@video@What is Unit Testing?](https://youtu.be/x95ez7_V7rA?si=JhCVhcEN7zZOkxdp)
 - [@feed@Explore top posts about Testing](https://app.daily.dev/tags/testing?ref=roadmapsh)