Fix search box position on the Add Plugins screen after resizing the window to narrower than 1000px and then back to wider than 1200px. Fixes #30658.
Built from https://develop.svn.wordpress.org/trunk@30830


git-svn-id: http://core.svn.wordpress.org/trunk@30820 1a063a9b-81f0-0310-95a4-ce76da25c4cd