Remove search bar in admin menu for logged in users.

[dufresnesteven]

When you are logged in, an admin bar appears at the top of the page. This admin bar includes a search function that searches the local site (globally for the main theme), which is different from the search bar in the header which is always a global search.

While this can be somewhat useful, most searchable sub-sites already have their own search bars on their pages and we therefore end up with 3 different search bar icons/controls.

Can we remove the admin bar search function?