Reduce clutter and repetive functionality from the initial landing page for...

Reduce clutter and repetive functionality from the initial landing page for installing plugins and themes by removing the tag/author/term dropdown.

The tag cloud (plugins) and feature filter (themes) is sufficient for tag functionality. All three "search by" fields are already weighted for a standard keyword search through the WP.org API.

fixes #19619 for 3.4.



git-svn-id: https://core.svn.wordpress.org/trunk@20592 1a063a9b-81f0-0310-95a4-ce76da25c4cd