removed .md from file url

Author: mikeblome

docs/linux/index.md

@@ -59,7 +59,7 @@ Use Visual Studio 2017 and later to create and debug applications running on Lin
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-                        <h3><a href="/cpp/overview/visual-cpp-in-visual-studio.md">C++ in Visual Studio</a></h3>
+                        <h3><a href="/cpp/overview/visual-cpp-in-visual-studio">C++ in Visual Studio</a></h3>
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