Protect: introduce new wp_robots_no_robots when available

wp_robots_no_robots() replaces wp_no_robots() in WP 5.7:
https://core.trac.wordpress.org/ticket/51511#comment:13

projects/plugins/jetpack/modules/protect/blocked-login-page.php

@@ -370,7 +370,11 @@ function display_page( $title, $message, $back_button = false, $recovery_form =
 			<meta http-equiv="Content-Type" content="text/html; charset=utf-8" />
 			<meta name="viewport" content="width=device-width">
 			<?php
-			if ( function_exists( 'wp_no_robots' ) ) {
+			// Remove wp_no_robots() when WordPress 5.7 is the minimum required version.
+			if ( function_exists( 'wp_robots' ) && function_exists( 'wp_robots_no_robots' ) && function_exists( 'add_filter' ) ) {
+				add_filter( 'wp_robots', 'wp_robots_no_robots' );
+				wp_robots();
+			} else {
 				wp_no_robots();
 			}
 			?>