Fix/remove search box and copy button

I noticed a couple features that no longer work:

- Search box (on site nav bar)
- Copy button (as seen on /examples & /help)

We should remove these feature (or if it's a quick fix, fix them) and also check for broken links. While updating this site to Batfish isn't on our roadmap, I think this is a fair in between step.

cc @colleenmcginnis 