Fix link (#42557)

Author: gewarren

docs/csharp/language-reference/keywords/extern.md

@@ -23,7 +23,7 @@ The `extern` keyword can also define an external assembly alias, which makes it
 
 It is an error to use the [abstract](abstract.md) and `extern` modifiers together to modify the same member. Using the `extern` modifier means that the method is implemented outside the C# code, whereas using the `abstract` modifier means that the method implementation is not provided in the class.
 
-The extern keyword has more limited uses in C# than in C++. To compare the C# keyword with the C++ keyword, see [Using extern to Specify Linkage](/cpp/cpp/extern-cpp.md#extern-c-and-extern-c-function-declarations) in the C++ Language Reference.
+The extern keyword has more limited uses in C# than in C++. To compare the C# keyword with the C++ keyword, see [Using extern to Specify Linkage](/cpp/cpp/extern-cpp#extern-c-and-extern-c-function-declarations) in the C++ Language Reference.
 
 ## Example 1