Less janky searching on mobile devices

Summary: Removes odd borders and padding, just a white search interface now.

Test Plan:
review at smaller breakpoints in sandbox, submit some items for search.

{F355209}

Reviewers: btrahan, epriestley

Reviewed By: epriestley

Subscribers: Korvin, epriestley

Differential Revision: https://secure.phabricator.com/D12221