Convert Swift Differentiable Programming Implementation Overview to Markdown

docs/DifferentiableProgramming.md

@@ -698,7 +698,7 @@ differentiation: given an "original function" to differentiate, a derivative
 function is generated by replacing function applications in the original
 function with corresponding derivative function applications. The algorithm is
 described in detail in the
-[Swift Differentiable Programming Implementation Overview document](http://bit.ly/swift-autodiff-internals).
+[Swift Differentiable Programming Implementation Overview](DifferentiableProgrammingImplementation.md).
 
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