You can't do anything about it. You can't control what headers google server sends.
I would even go so far as to say it is reporting a false positive that you should fix.
http://redbot.org/?uri=http%3A%2F%2Ffonts.googleapis.com%2Fcss%3Ffamily%3DOpen%2BSans%3A400%2C800
As you can see the resource is cached, has a max age header and is even compressed.
You site is fast enough! I wouldn't worry about getting 100. You can probably stop optimizing it.
But if you want to tinker some more, here's a few ideas on improving things, I ran a report: http://www.webpagetest.org/result/130703_H7_15KM/
- I would have your server send a 204 No Content header for your non-existent favicon.ico file OR make one and add it so there's no 404 on the resource.
- Use a CDN for your resources
- Use progressive jpegs and optimize the ones you're using