[gn build] Port 6897ca4

Author: llvmgnsyncbot

llvm/utils/gn/secondary/libcxx/include/BUILD.gn

@@ -1104,14 +1104,12 @@ if (current_toolchain == default_toolchain) {
       "__fwd/get.h",
       "__fwd/ios.h",
       "__fwd/istream.h",
-      "__fwd/map.h",
       "__fwd/mdspan.h",
       "__fwd/memory.h",
       "__fwd/memory_resource.h",
       "__fwd/ostream.h",
       "__fwd/pair.h",
       "__fwd/queue.h",
-      "__fwd/set.h",
       "__fwd/span.h",
       "__fwd/sstream.h",
       "__fwd/stack.h",