Your code works for me in version 4.7.2 with 2016 theme, but a slightly simpler version is to remove the action entirely rather than filter the output:
remove_action( 'wp_head', 'wp_generator' );
Your code works for me in version 4.7.2 with 2016 theme, but a slightly simpler version is to remove the action entirely rather than filter the output:
remove_action( 'wp_head', 'wp_generator' );