Themes: Update the theme count when searching for installed themes, like we do on Add Themes screen.

props afercia.
see #26600.

git-svn-id: https://develop.svn.wordpress.org/trunk@31495 602fd350-edb4-49c9-b593-d223f7449a82

src/wp-admin/js/theme.js

@@ -828,7 +828,7 @@ themes.view.Themes = wp.Backbone.View.extend({
 	index: 0,
 
 	// The theme count element
-	count: $( '.wp-filter .theme-count' ),
+	count: $( '.wp-core-ui .theme-count' ),
 
 	initialize: function( options ) {
 		var self = this;