reduce useless extend code

DeflateReadBodyMixin#each_fragment is overwritten by extend
DirectReadBodyMixin(l143).
And, we can't use DeflateReadBodyMixin#each_fragment,
because, we need compressed fragment size.

lib/td/client/api/job.rb

@@ -140,14 +140,8 @@ def job_result_format(job_id, format, io=nil, &block)
           raise_error("Get job result failed", res)
         end
 
-        if ce = res.header['Content-Encoding']
-          res.extend(DeflateReadBodyMixin)
-          res.gzip = true if ce == 'gzip'
-        else
-          res.extend(DirectReadBodyMixin)
-        end
-
         res.extend(DirectReadBodyMixin)
+
         if ce = res.header['Content-Encoding']
           if ce == 'gzip'
             infl = Zlib::Inflate.new(Zlib::MAX_WBITS + 16)