How to Hide Gutenberg Admin Menus

function plt_hide_gutenberg_menus() {
	//Hide "Appearance → Fonts".
	remove_submenu_page('themes.php', 'font-library-wp-admin');
	//Hide "Settings → Connectors".
	remove_submenu_page('options-general.php', 'options-connectors-wp-admin');

	//Hide "Gutenberg".
	remove_menu_page('gutenberg');
	//Hide "Gutenberg → Demo".
	remove_submenu_page('gutenberg', 'gutenberg');
	//Hide "Gutenberg → Support".
	remove_submenu_page('gutenberg', 'https://wordpress.org/support/plugin/gutenberg');
	//Hide "Gutenberg → Documentation".
	remove_submenu_page('gutenberg', 'https://developer.wordpress.org/block-editor');
	//Hide "Gutenberg → Experiments".
	remove_submenu_page('gutenberg', 'experiments-wp-admin');
}

add_action('admin_menu', 'plt_hide_gutenberg_menus', 101);
Where do I put this code?