Merge pull request #2269 from bjacobel/bjacobel/documentation-pagination-readonlyfield

Change serializers.Field to serializers.ReadOnlyField for 3.x compatibility

docs/api-guide/pagination.md

@@ -128,7 +128,7 @@ For example, to nest a pair of links labelled 'prev' and 'next', and set the nam
 
     class CustomPaginationSerializer(pagination.BasePaginationSerializer):
         links = LinksSerializer(source='*')  # Takes the page object as the source
-        total_results = serializers.Field(source='paginator.count')
+        total_results = serializers.ReadOnlyField(source='paginator.count')
 
         results_field = 'objects'