Remove search box from main nav when on the search page.

[benlk]

Changes

• Removes the search box from the main nav when on the search page

before:

after:

Why

Because I noticed the duplication while working on https://github.com/INN/largo/issues/1602

Questions

• [x] Are we planning on keeping the main nav search item?
• [x] should this PR be against a different branch than master? @tylermachado I know you have work going on in #93; should this PR be against that branch?

[tylermachado]

1. Yes on keeping the main nav search item.
2. I think so; work continues on that branch at the moment.

[benlk]

Is it okay to merge this?