Revert "Fixed XPath AST for :last-of-type"

Axes can't be used in combination with functions.

This reverts commit b0b572a584.

lib/oga/css/parser.y

@@ -528,11 +528,7 @@ end
   # @return [AST::Node]
   #
   def on_pseudo_class_last_of_type
-    return s(
-      :eq,
-      s(:call, 'count', s(:axis, 'following-sibling', s(:call, 'name'))),
-      s(:int, 0)
-    )
+    return s(:eq, s(:call, 'position'), s(:call, 'last'))
   end
 
   ##

spec/oga/css/parser/pseudo_classes/last_of_type_spec.rb

@@ -4,7 +4,7 @@ describe Oga::CSS::Parser do
   context ':last-of-type pseudo class' do
     example 'parse the :last-of-type pseudo class' do
       parse_css(':last-of-type').should == parse_xpath(
-        'descendant::*[count(following-sibling::name()) = 0]'
+        'descendant::*[position() = last()]'
       )
     end
   end