Customizer Theme Switcher: Remove "Add New" references.

The current iteration takes you out of the customizer context, which isn't great UX and doesn't really fit into the flows targeted by this particular UI.

fixes #31837.

git-svn-id: https://develop.svn.wordpress.org/trunk@31968 602fd350-edb4-49c9-b593-d223f7449a82

src/wp-includes/class-wp-customize-control.php

@@ -1234,34 +1234,6 @@ class WP_Customize_Theme_Control extends WP_Customize_Control {
 	}
 }
 
-/**
- * Customize New Theme Control class.
- *
- * @since 4.2.0
- *
- * @see WP_Customize_Control
- */
-class WP_Customize_New_Theme_Control extends WP_Customize_Control {
-
-	/**
-	 * Render the control content.
-	 *
-	 * @since 4.2.0
-	 */
-	public function render_content() {
-		?>
-		<div class="theme add-new-theme">
-			<a href="<?php echo admin_url( 'theme-install.php' ); ?>" target="_top">
-				<div class="theme-screenshot">
-					<span></span>
-				</div>
-				<h3 class="theme-name"><?php _e( 'Add New Theme' ); ?></h3>
-			</a>
-		</div>
-		<?php
-	}
-}
-
 /**
  * Widget Area Customize Control class.
  *