Clean up Space select/dropdown UI alignment
Summary: This alignment is off on edit forms, from the new overflow rules. Let's re-align everything for forms too.
Add 2 new spaces, go to Maniphest, edit a task, see proper alignment of [Space] [Policy] view dropdowns. Check mobile alignment and Safari/FF.
Reviewed By: epriestley
Differential Revision: https://secure.phabricator.com/D17491