Try increasing read_timeout a little more

It failed again
http://ci.rvm.jp/results/trunk-mjit-wait@silicon-docker/3018488

Author: k0kubun

test/net/http/test_httpresponse.rb

@@ -88,7 +88,7 @@ def test_read_body_block_mod
         :ok
       end
       io = Net::BufferedIO.new(r)
-      io.read_timeout *= 5 if RubyVM::MJIT.enabled? # for --jit-wait
+      io.read_timeout *= 10 if RubyVM::MJIT.enabled? # for --jit-wait
       res = Net::HTTPResponse.read_new(io)
       nr = 0
       res.reading_body io, true do