Note that you must change "plugins.php" to match whatever page you want to allow.

heartbeat_allowed.php

<?php
/**
 * Plugin Name: Allow Heartbeat for Gravity Forms on WP Enting
 * Plugin URI: https://gist.github.com/desrosj/409a17b718f07d1190b7
 * Description: Allow the Heartbeat API on Gravity Form related edit pages on WP Engine. Fork of https://gist.github.com/JPry/b1f6c55a5d5337557f97
 * Version: 1.0
 * Author: Jonathan Desrosiers
 * Author URI: http://jonathandesrosiers.com/
 * License: GPL2
 */

// Prevent direct access to this file
if ( ! defined( 'ABSPATH' ) ) {
	die( "You can't do anything by accessing this file directly." );
}

/**
 * Add a page to the list of pages where the Heartbeat API is allowed.
 * 
 * Replace plugins.php with the actual page name. The page name correlates to the global $pagenow variable.
 * See http://codex.wordpress.org/Global_Variables#Admin_Globals for more information about this
 * global variable.
 *
 * @param array $heartbeat_allowed_pages The array of pages where the Heartbeat API is allowed.
 * @return array The updated array of pages where the Heartbeat API is allowed.
 */
function gform_add_heartbeat_allowed_page( $heartbeat_allowed_pages ) {
    $heartbeat_allowed_pages[] = 'admin.php';
    return $heartbeat_allowed_pages;
}
add_filter( 'wpe_heartbeat_allowed_pages', 'gform_add_heartbeat_allowed_page' );