Update the link of youtube channel (#4261)

Updated the link of youtube channel in c++ roadmap, what is c++

src/data/roadmaps/cpp/content/100-introduction/100-what-is-cpp.md

@@ -45,6 +45,6 @@ int main() {
 
 In the above program, we define a simple function `add` and a class `Calculator` with a member function `multiply`. The `main` function demonstrates how to use these to perform basic arithmetic.
 
-- [C++ Tutorial for Beginners - Full Course](https://www.youtube.com/watch?v=vlnpwxzdw4y)
+- [C++ Tutorial for Beginners - Full Course](https://youtu.be/vLnPwxZdW4Y)
 - [w3schools C++ tutorial](https://www.w3schools.com/cpp/)
 - [Learn C++](https://www.learncpp.com/)