How to Hide the "Replace Asset Source" Admin Menu

function plt_hide_replace_third_party_asset_source_menus() {
	//Hide the "Settings → Replace Asset Source" menu.
	remove_submenu_page('options-general.php', 'replace-third-party-asset-source-setting');
}

add_action('admin_menu', 'plt_hide_replace_third_party_asset_source_menus', 11);

Where do I put this code?