[gn] port a6ba74e

Author: nico

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

@@ -643,7 +643,6 @@ if (current_toolchain == default_toolchain) {
       "__ranges/views.h",
       "__ranges/zip_view.h",
       "__split_buffer",
-      "__std_stream",
       "__string/char_traits.h",
       "__string/constexpr_c_functions.h",
       "__string/extern_template_lists.h",