Okay, here is the final answer so you DO NOT need to edit any Gravity plugin form files or install additional plugins:
function remove_gravity_forms_nag() {
update_option( 'rg_gforms_message', '' );
remove_action( 'after_plugin_row_gravityforms/gravityforms.php', array( 'GFForms', 'plugin_row' ) );
}
add_action( 'admin_init', 'remove_gravity_forms_nag' );Just copy and paste into your own plugin or theme functions.php file!
