Docs: Add missing @global entry for list table view mode in WP_Screen::render_view_mode().

Props priyankabehera155.
See #40208.

git-svn-id: https://develop.svn.wordpress.org/trunk@40308 602fd350-edb4-49c9-b593-d223f7449a82

src/wp-admin/includes/class-wp-screen.php

@@ -1193,6 +1193,8 @@ final class WP_Screen {
 	 * Render the list table view mode preferences.
 	 *
 	 * @since 4.4.0
+	 *
+	 * @global string $mode List table view mode.
 	 */
 	public function render_view_mode() {
 		$screen = get_current_screen();