Update LearnConcurrency.md

The link to [Simulating a Real-World System in Go] is broken, so I’ve updated it with the new link in Youtube.

Author: Standing-Man

LearnConcurrency.md

@@ -6,7 +6,7 @@ This page links to resources for learning about concurrency in Go.  The items ar
 
 ## Beginner
 - Read [Effective Go: Concurrency](https://go.dev/doc/effective_go#concurrency)
-- Watch [Simulating a real-world system in Go](https://www.dotconferences.com/2017/11/sameer-ajmani-simulating-a-real-world-system-in-go)
+- Watch [Simulating a real-world system in Go](https://www.youtube.com/watch?v=_YK0viplIl4)
 - Study [The Go Programming Language Specification](https://go.dev/ref/spec), especially
     - [Go statements](https://go.dev/ref/spec#Go_statements)
     - [Channel types](https://go.dev/ref/spec#Channel_types)