Use a more specific selector for the count displayed on Add Themes network admin screen.

props mantismamita, nikolov.tmw.
fixes #29421.

git-svn-id: https://develop.svn.wordpress.org/trunk@29786 602fd350-edb4-49c9-b593-d223f7449a82

src/wp-admin/js/theme.js

@@ -824,7 +824,7 @@ themes.view.Themes = wp.Backbone.View.extend({
 	index: 0,
 
 	// The theme count element
-	count: $( '.theme-count' ),
+	count: $( '.wp-filter .theme-count' ),
 
 	initialize: function( options ) {
 		var self = this;