clean up two tests

test/mini_racer_test.rb

@@ -102,15 +102,14 @@ def test_it_can_stop
   end
 
   def test_it_can_timeout_during_serialization
-    context = MiniRacer::Context.new(timeout: 500)
+    context = MiniRacer::Context.new(timeout: 20)
 
     assert_raises(MiniRacer::ScriptTerminatedError) do
       context.eval 'var a = {get a(){ while(true); }}; a'
     end
   end
 
-  def test_it_can_automatically_time_out_context
-    # 2 millisecs is a very short timeout but we don't want test running forever
+  def test_it_can_time_out_js_eval
     context = MiniRacer::Context.new(timeout: 2)
     assert_raises do
       context.eval('while(true){}')