Revert "Fix anchor link"

This reverts commit 1474fcd.

As of dlang-tour/core#783, we should be able to use URL fragments to link to
specific headings, so the previous version of the code (that used them) is
preferrable.

gems/functional-programming.md

@@ -4,7 +4,7 @@ D puts an emphasis on *functional programming* and provides
 first-class support for development
 in a functional style. See:
 * [immutable](basics/type-qualifiers) type qualifier
-* [delegates](basics/delegates)
+* [anonymous functions](basics/delegates#anonymous-functions-lambdas)
 * [range algorithms](gems/range-algorithms)
 
 ## Pure functions