Update content: Add source attribution to Khan Academy link in CS roadmap

Added Khan Academy attribution to combinatorics resource for better clarity.

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Co-Authored-By: Claude <noreply@anthropic.com>

src/data/roadmaps/computer-science/content/combinatorics@lWnAY0DgrUOmT6yqnxeBN.md

@@ -4,7 +4,7 @@ Combinatorics is the study of counting. It is a branch of mathematics that is us
 
 Visit the following resources to learn more:
 
-- [@article@Probability and Combinatorics](https://www.khanacademy.org/math/probability/probability-and-combinatorics-topic)
+- [@article@Probability and Combinatorics - Khan Academy](https://www.khanacademy.org/math/probability/probability-and-combinatorics-topic)
 - [@video@Math Skills: How to find Factorial, Permutation and Combination](https://www.youtube.com/watch?v=8RRo6Ti9d0U)
 - [@video@Make School: Probability](https://www.youtube.com/watch?v=sZkAAk9Wwa4)
 - [@video@Make School: More Probability and Markov Chains](https://www.youtube.com/watch?v=dNaJg-mLobQ)