Removed extra throw from following-sibling()

I can't quite recall why this throw was present in the Evaluator in the
first place, but removing it doesn't seem to break anything (in the
Evaluator). In fact, removing it actually fixes some of the CSS specs
that were broken when using the Compiler.

lib/oga/xpath/compiler.rb

@@ -304,9 +304,7 @@ module Oga
                 end
                 .followed_by do
                   backup_variable(node, doc_node) do
-                    process(ast, node, &block).if_true do
-                      yield(node).followed_by(throw_message(:skip_children))
-                    end
+                    process(ast, node, &block).if_true { yield node }
                   end
                 end
             end